title: “ANALISIS PEUBAH-PEUBAH YANG MEMENGARUHI ANGKA PARTISIPASI SEKOLAH (APS) TINGKAT
SMA MENURUT PROVINSI DI INDONESIA”
author: “DIVA NISFU MUSTIKA”
date: “2023-08-01”
output: html_document

Input Data

library(readxl)
setwd("C:\\Users\\Diva\\Documents\\anreg")
data <- read_excel("tugasakhir.xlsx")
data
## # A tibble: 34 × 9
##        y    x1    x2    x3    x4     x5    x6    x7    x8
##    <dbl> <dbl> <dbl> <dbl> <dbl>  <dbl> <dbl> <dbl> <dbl>
##  1  83.1  245.  98.2  33.2 14.8  26064.  72.8  9.79   693
##  2  78.7  358.  99.1  56.3  8.33 37944.  72.7  9.99   982
##  3  83.7  451.  99.3  49.6  6.04 32378.  73.3  9.51   212
##  4  77.3  366.  99.2  40.1  6.84 80058.  73.5  9.54   389
##  5  72.5  328.  98.1  33.3  7.7  44536.  72.1  9.07   203
##  6  70.9  347.  98.6  37.3 12.0  39677.  70.9  8.82   340
##  7  79.3  360.  97.8  32.6 14.3  24230.  72.2  9.28   175
##  8  71.1  317.  97.2  31.3 11.4  28064.  70.4  8.61   225
##  9  68.4  422.  98.2  56    4.61 38674.  72.2  8.57    23
## 10  84.5  334.  99.0  83.3  6.03 87238.  76.5 10.5     31
## # ℹ 24 more rows
summary(data)
##        y               x1              x2              x3        
##  Min.   :65.93   Min.   :198.6   Min.   :81.19   Min.   : 23.00  
##  1st Qu.:70.83   1st Qu.:288.1   1st Qu.:95.25   1st Qu.: 33.52  
##  Median :74.43   Median :341.6   Median :98.13   Median : 42.10  
##  Mean   :75.14   Mean   :343.7   Mean   :96.69   Mean   : 47.64  
##  3rd Qu.:78.94   3rd Qu.:364.9   3rd Qu.:98.92   3rd Qu.: 55.67  
##  Max.   :89.95   Max.   :576.8   Max.   :99.81   Max.   :100.00  
##        x4               x5               x6              x7        
##  Min.   : 4.530   Min.   : 13299   Min.   :65.89   Min.   : 7.310  
##  1st Qu.: 6.388   1st Qu.: 28139   1st Qu.:70.32   1st Qu.: 8.580  
##  Median : 8.495   Median : 37164   Median :72.23   Median : 9.225  
##  Mean   :10.299   Mean   : 45361   Mean   :72.43   Mean   : 9.247  
##  3rd Qu.:12.213   3rd Qu.: 41988   3rd Qu.:73.31   3rd Qu.: 9.777  
##  Max.   :26.800   Max.   :182909   Max.   :81.65   Max.   :11.300  
##        x8       
##  Min.   :  8.0  
##  1st Qu.:109.0  
##  Median :209.5  
##  Mean   :295.7  
##  3rd Qu.:389.8  
##  Max.   :982.0

Pemodelan Awal

model <- lm(y ~ x1+x2+x3+x4+x5+x6+x7+x8, data=data)
model
## 
## Call:
## lm(formula = y ~ x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8, data = data)
## 
## Coefficients:
## (Intercept)           x1           x2           x3           x4           x5  
##  15.7040209    0.0158719   -0.5700555   -0.1055390    0.1588718   -0.0000745  
##          x6           x7           x8  
##   0.5541543    8.3259564   -0.0042476
summary(model)
## 
## Call:
## lm(formula = y ~ x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8, data = data)
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -7.0249 -2.7384 -0.3461  1.9034  9.0973 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept)  1.570e+01  3.156e+01   0.498   0.6231    
## x1           1.587e-02  1.168e-02   1.358   0.1865    
## x2          -5.701e-01  3.275e-01  -1.741   0.0940 .  
## x3          -1.055e-01  6.934e-02  -1.522   0.1405    
## x4           1.589e-01  1.941e-01   0.818   0.4208    
## x5          -7.450e-05  2.821e-05  -2.641   0.0140 *  
## x6           5.542e-01  2.615e-01   2.119   0.0442 *  
## x7           8.326e+00  1.668e+00   4.990 3.82e-05 ***
## x8          -4.248e-03  2.849e-03  -1.491   0.1485    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 4.009 on 25 degrees of freedom
## Multiple R-squared:  0.644,  Adjusted R-squared:  0.5301 
## F-statistic: 5.653 on 8 and 25 DF,  p-value: 0.0003781
anova(model)
## Analysis of Variance Table
## 
## Response: y
##           Df Sum Sq Mean Sq F value    Pr(>F)    
## x1         1   0.12    0.12  0.0072   0.93284    
## x2         1  67.27   67.27  4.1865   0.05140 .  
## x3         1  31.67   31.67  1.9709   0.17265    
## x4         1  74.65   74.65  4.6455   0.04096 *  
## x5         1   4.39    4.39  0.2734   0.60565    
## x6         1 101.30  101.30  6.3047   0.01887 *  
## x7         1 411.61  411.61 25.6161 3.181e-05 ***
## x8         1  35.71   35.71  2.2223   0.14854    
## Residuals 25 401.71   16.07                      
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Eksplorasi Data

boxplot(data$y, col='blue')

Uji Multikololinieritas

car::vif(model)
##       x1       x2       x3       x4       x5       x6       x7       x8 
## 1.826024 2.975033 3.400991 2.162116 1.889130 1.735735 3.819614 1.115202
library(mctest)
imcdiag(model, method = "VIF", vif=10)
## 
## Call:
## imcdiag(mod = model, method = "VIF", vif = 10)
## 
## 
##  VIF Multicollinearity Diagnostics
## 
##       VIF detection
## x1 1.8260         0
## x2 2.9750         0
## x3 3.4010         0
## x4 2.1621         0
## x5 1.8891         0
## x6 1.7357         0
## x7 3.8196         0
## x8 1.1152         0
## 
## NOTE:  VIF Method Failed to detect multicollinearity
## 
## 
## 0 --> COLLINEARITY is not detected by the test
## 
## ===================================
mc.plot(model, vif = 10)

library(olsrr)
## 
## Attaching package: 'olsrr'
## The following object is masked from 'package:datasets':
## 
##     rivers

ols_vif_tol(model)
##   Variables Tolerance      VIF
## 1        x1 0.5476381 1.826024
## 2        x2 0.3361307 2.975033
## 3        x3 0.2940320 3.400991
## 4        x4 0.4625099 2.162116
## 5        x5 0.5293443 1.889130
## 6        x6 0.5761249 1.735735
## 7        x7 0.2618065 3.819614
## 8        x8 0.8966988 1.115202

DETEKSI PENCILAN, LEVERAGE, DAN AMATAN BERPENGARUH

plot(model, which=5)
olsrr:: ols_plot_diagnostics(model)

ols_plot_resid_lev(model)

#menghitung s, ei,n, dan p
s = sqrt(16.07)
s #s adalah akar dari KTG
## [1] 4.00874
ei = model$residuals
ei
##             1             2             3             4             5 
##  3.7017200701  1.9180751264  5.2618096126  2.9301184082 -1.4829850779 
##             6             7             8             9            10 
## -0.3332973169  0.0958480839 -0.3588524251 -1.2561917436  4.9863298306 
##            11            12            13            14            15 
## -7.0248618843 -2.4138814839 -3.0913864156  4.8113214322  0.2201472886 
##            16            17            18            19            20 
## -4.4433830509  1.0101372613  1.8593127532  4.3250833567  4.2634455842 
##            21            22            23            24            25 
## -3.3215160084 -1.2242131449  9.0973429737 -0.0007716985 -2.8675858041 
##            26            27            28            29            30 
## -0.3070349555 -2.8465429078 -5.7996880159 -0.3588824871 -3.1542853457 
##            31            32            33            34 
## -3.2049617562  1.2891920047 -1.4300473322 -0.8495149320
n = dim(data)[1]
n
## [1] 34
p = length(model$coefficients)
p
## [1] 9
# menghitung hii dan ri
xbar = mean(data$x1+data$x2+data$x3+data$x4+data$x5+data$x6+data$x7+data$x8)
hii=hatvalues(model)
ri = ei/(s*sqrt(1-hii))
Obs = c(1:n)
summ <- cbind.data.frame(Obs, hii)
View(summ)

#Hapus Pencilan

model_tanpa_11 = lm((y) ~ x1+x2+x3+x4+x5+x6+x7+x8, data=data[-c(23),])
summary(model_tanpa_11)
## 
## Call:
## lm(formula = (y) ~ x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8, data = data[-c(23), 
##     ])
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -6.2103 -2.1795 -0.2243  1.2244  6.5421 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept)  3.664e-01  2.724e+01   0.013 0.989377    
## x1           1.487e-02  9.938e-03   1.496 0.147616    
## x2          -6.122e-01  2.787e-01  -2.197 0.037951 *  
## x3          -1.247e-01  5.924e-02  -2.106 0.045878 *  
## x4           1.456e-01  1.651e-01   0.882 0.386574    
## x5          -1.167e-04  2.726e-05  -4.281 0.000258 ***
## x6           8.182e-01  2.366e-01   3.458 0.002046 ** 
## x7           8.655e+00  1.422e+00   6.087 2.75e-06 ***
## x8          -3.726e-03  2.428e-03  -1.535 0.137920    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 3.408 on 24 degrees of freedom
## Multiple R-squared:  0.7438, Adjusted R-squared:  0.6583 
## F-statistic: 8.708 on 8 and 24 DF,  p-value: 1.626e-05
anova(model_tanpa_11)
## Analysis of Variance Table
## 
## Response: (y)
##           Df Sum Sq Mean Sq F value    Pr(>F)    
## x1         1   0.11    0.11  0.0096 0.9228727    
## x2         1  56.95   56.95  4.9042 0.0365371 *  
## x3         1  20.90   20.90  1.8000 0.1922721    
## x4         1  75.77   75.77  6.5250 0.0174034 *  
## x5         1  17.84   17.84  1.5360 0.2271925    
## x6         1 168.08  168.08 14.4736 0.0008624 ***
## x7         1 441.94  441.94 38.0567 2.252e-06 ***
## x8         1  27.35   27.35  2.3555 0.1379197    
## Residuals 24 278.70   11.61                      
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
model_tanpa_23 = lm((y) ~ x1+x2+x3+x4+x5+x6+x7+x8, data=data[-c(11),])
summary(model_tanpa_23)
## 
## Call:
## lm(formula = (y) ~ x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8, data = data[-c(11), 
##     ])
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -5.6821 -2.3169 -0.3876  1.7406  5.8432 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept)  5.539e+00  2.733e+01   0.203   0.8411    
## x1           1.709e-02  1.006e-02   1.699   0.1022    
## x2          -5.760e-01  2.816e-01  -2.045   0.0520 .  
## x3          -8.576e-02  5.997e-02  -1.430   0.1656    
## x4           2.209e-01  1.681e-01   1.314   0.2014    
## x5          -2.214e-05  2.947e-05  -0.752   0.4596    
## x6           6.186e-01  2.258e-01   2.739   0.0114 *  
## x7           8.520e+00  1.436e+00   5.932 4.03e-06 ***
## x8          -2.944e-03  2.486e-03  -1.185   0.2478    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 3.448 on 24 degrees of freedom
## Multiple R-squared:  0.7451, Adjusted R-squared:  0.6601 
## F-statistic: 8.768 on 8 and 24 DF,  p-value: 1.536e-05
anova(model_tanpa_23)
## Analysis of Variance Table
## 
## Response: (y)
##           Df Sum Sq Mean Sq F value    Pr(>F)    
## x1         1   0.40    0.40  0.0333  0.856744    
## x2         1  76.38   76.38  6.4260  0.018179 *  
## x3         1  81.84   81.84  6.8860  0.014869 *  
## x4         1  87.57   87.57  7.3679  0.012101 *  
## x5         1  18.30   18.30  1.5396  0.226665    
## x6         1 124.61  124.61 10.4840  0.003503 ** 
## x7         1 427.88  427.88 36.0008 3.407e-06 ***
## x8         1  16.68   16.68  1.4031  0.247806    
## Residuals 24 285.25   11.89                      
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
model_tanpa_11_23 = lm((y) ~ x1+x2+x3+x4+x5+x6+x7+x8, data=data[-c(11,23),])
summary(model_tanpa_11_23)
## 
## Call:
## lm(formula = (y) ~ x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8, data = data[-c(11, 
##     23), ])
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -5.9983 -2.0342 -0.2959  1.3315  6.0570 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept) -6.298e-01  2.632e+01  -0.024  0.98112    
## x1           1.596e-02  9.624e-03   1.658  0.11088    
## x2          -6.014e-01  2.693e-01  -2.233  0.03557 *  
## x3          -1.061e-01  5.835e-02  -1.818  0.08210 .  
## x4           1.881e-01  1.616e-01   1.164  0.25631    
## x5          -7.026e-05  3.860e-05  -1.820  0.08179 .  
## x6           7.676e-01  2.307e-01   3.328  0.00293 ** 
## x7           8.662e+00  1.374e+00   6.305 1.96e-06 ***
## x8          -3.105e-03  2.375e-03  -1.307  0.20403    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 3.292 on 23 degrees of freedom
## Multiple R-squared:  0.769,  Adjusted R-squared:  0.6887 
## F-statistic: 9.571 on 8 and 23 DF,  p-value: 9.58e-06
anova(model_tanpa_11_23)
## Analysis of Variance Table
## 
## Response: (y)
##           Df Sum Sq Mean Sq F value    Pr(>F)    
## x1         1   0.36    0.36  0.0336  0.856138    
## x2         1  65.08   65.08  6.0039  0.022302 *  
## x3         1  62.45   62.45  5.7614  0.024870 *  
## x4         1  87.54   87.54  8.0761  0.009236 ** 
## x5         1   9.52    9.52  0.8779  0.358506    
## x6         1 145.82  145.82 13.4519  0.001279 ** 
## x7         1 440.67  440.67 40.6528 1.661e-06 ***
## x8         1  18.53   18.53  1.7090  0.204029    
## Residuals 23 249.31   10.84                      
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

##Uji Asumsi

#uji kehomogenan ragam
library(ggplot2)

library(dplyr)
## 
## Attaching package: 'dplyr'
## The following objects are masked from 'package:stats':
## 
##     filter, lag
## The following objects are masked from 'package:base':
## 
##     intersect, setdiff, setequal, union
data.frame(rstandard(model_tanpa_11_23),
           model_tanpa_11_23$fitted.values) %>%
  ggplot(aes(x = model_tanpa_11_23$fitted.values, y = rstandard(model_tanpa_11_23))) + 
  geom_point() +
  geom_hline(yintercept = 0, linetype = "dotted") +
  labs(title = "Standardized Residuals vs Fitted Values Plot")

plot(model_tanpa_11_23,1)

library(lmtest)
## Loading required package: zoo
## 
## Attaching package: 'zoo'
## The following objects are masked from 'package:base':
## 
##     as.Date, as.Date.numeric
bptest(model_tanpa_11_23)
## 
##  studentized Breusch-Pagan test
## 
## data:  model_tanpa_11_23
## BP = 3.2343, df = 8, p-value = 0.9188
#nilai harapan = nol
t.test(resid(model_tanpa_11_23), mu = 0,) 
## 
##  One Sample t-test
## 
## data:  resid(model_tanpa_11_23)
## t = 1.2057e-17, df = 31, p-value = 1
## alternative hypothesis: true mean is not equal to 0
## 95 percent confidence interval:
##  -1.022456  1.022456
## sample estimates:
##    mean of x 
## 6.044427e-18
#h0: nilai harapan sisaan=0

#cek autokorelasi
lmtest::dwtest(data$y~data$x1 + data$x2+data$x3+data$x4+data$x5+data$x6+data$x7+data$x8) #h0:tidak ada auto korelasi
## 
##  Durbin-Watson test
## 
## data:  data$y ~ data$x1 + data$x2 + data$x3 + data$x4 + data$x5 + data$x6 +     data$x7 + data$x8
## DW = 1.83, p-value = 0.2098
## alternative hypothesis: true autocorrelation is greater than 0
plot(x = 1:dim(data)[1],
     y = model$residuals,
     type = 'b', 
     ylab = "Residuals",
     xlab = "Observation")       # plot sisaan vs urutan

# Uji kenormalan
plot(model_tanpa_11_23,2)

shapiro.test(residuals(model_tanpa_11_23)) 
## 
##  Shapiro-Wilk normality test
## 
## data:  residuals(model_tanpa_11_23)
## W = 0.97586, p-value = 0.6736
#ho: sisaan menyebar normal

###Pemilihan model terbaik

library(MASS)
## 
## Attaching package: 'MASS'
## The following object is masked from 'package:dplyr':
## 
##     select
## The following object is masked from 'package:olsrr':
## 
##     cement
#---Stepwise Regression Model----
step.model<- stepAIC(model_tanpa_11_23, direction = "both", trace = FALSE)
summary(step.model)
## 
## Call:
## lm(formula = (y) ~ x1 + x2 + x3 + x5 + x6 + x7, data = data[-c(11, 
##     23), ])
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -6.2499 -1.9316  0.1917  1.3188  5.2738 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept)  1.187e+01  2.186e+01   0.543  0.59199    
## x1           1.680e-02  9.730e-03   1.727  0.09653 .  
## x2          -7.330e-01  2.229e-01  -3.288  0.00299 ** 
## x3          -1.353e-01  5.453e-02  -2.480  0.02021 *  
## x5          -7.124e-05  3.783e-05  -1.883  0.07138 .  
## x6           7.359e-01  2.330e-01   3.158  0.00412 ** 
## x7           9.168e+00  1.324e+00   6.924 2.94e-07 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 3.338 on 25 degrees of freedom
## Multiple R-squared:  0.7419, Adjusted R-squared:   0.68 
## F-statistic: 11.98 on 6 and 25 DF,  p-value: 2.513e-06
anova(step.model)
## Analysis of Variance Table
## 
## Response: (y)
##           Df Sum Sq Mean Sq F value    Pr(>F)    
## x1         1   0.36    0.36  0.0327  0.857946    
## x2         1  65.08   65.08  5.8416  0.023278 *  
## x3         1  62.45   62.45  5.6057  0.025950 *  
## x5         1   1.41    1.41  0.1265  0.725027    
## x6         1 137.31  137.31 12.3251  0.001719 ** 
## x7         1 534.14  534.14 47.9447 2.941e-07 ***
## Residuals 25 278.52   11.14                      
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#---Backward Regression Model----
model1_tanpa_11_23 = glm((y) ~ x1+x2+x3+x4+x5+x6+x7+x8, data=data[-c(11,23),])
summary(model1_tanpa_11_23)
## 
## Call:
## glm(formula = (y) ~ x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8, data = data[-c(11, 
##     23), ])
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept) -6.298e-01  2.632e+01  -0.024  0.98112    
## x1           1.596e-02  9.624e-03   1.658  0.11088    
## x2          -6.014e-01  2.693e-01  -2.233  0.03557 *  
## x3          -1.061e-01  5.835e-02  -1.818  0.08210 .  
## x4           1.881e-01  1.616e-01   1.164  0.25631    
## x5          -7.026e-05  3.860e-05  -1.820  0.08179 .  
## x6           7.676e-01  2.307e-01   3.328  0.00293 ** 
## x7           8.662e+00  1.374e+00   6.305 1.96e-06 ***
## x8          -3.105e-03  2.375e-03  -1.307  0.20403    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## (Dispersion parameter for gaussian family taken to be 10.83978)
## 
##     Null deviance: 1079.28  on 31  degrees of freedom
## Residual deviance:  249.31  on 23  degrees of freedom
## AIC: 176.51
## 
## Number of Fisher Scoring iterations: 2
back.model <- stepAIC(model_tanpa_11_23, direction = "backward", trace =  FALSE)
summary(back.model)
## 
## Call:
## lm(formula = (y) ~ x1 + x2 + x3 + x5 + x6 + x7, data = data[-c(11, 
##     23), ])
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -6.2499 -1.9316  0.1917  1.3188  5.2738 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept)  1.187e+01  2.186e+01   0.543  0.59199    
## x1           1.680e-02  9.730e-03   1.727  0.09653 .  
## x2          -7.330e-01  2.229e-01  -3.288  0.00299 ** 
## x3          -1.353e-01  5.453e-02  -2.480  0.02021 *  
## x5          -7.124e-05  3.783e-05  -1.883  0.07138 .  
## x6           7.359e-01  2.330e-01   3.158  0.00412 ** 
## x7           9.168e+00  1.324e+00   6.924 2.94e-07 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 3.338 on 25 degrees of freedom
## Multiple R-squared:  0.7419, Adjusted R-squared:   0.68 
## F-statistic: 11.98 on 6 and 25 DF,  p-value: 2.513e-06
anova(back.model)
## Analysis of Variance Table
## 
## Response: (y)
##           Df Sum Sq Mean Sq F value    Pr(>F)    
## x1         1   0.36    0.36  0.0327  0.857946    
## x2         1  65.08   65.08  5.8416  0.023278 *  
## x3         1  62.45   62.45  5.6057  0.025950 *  
## x5         1   1.41    1.41  0.1265  0.725027    
## x6         1 137.31  137.31 12.3251  0.001719 ** 
## x7         1 534.14  534.14 47.9447 2.941e-07 ***
## Residuals 25 278.52   11.14                      
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#---Forward Regression Model----
fwd.model <- stepAIC(model_tanpa_11_23, direction = "forward", trace = FALSE)
summary(fwd.model)
## 
## Call:
## lm(formula = (y) ~ x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8, data = data[-c(11, 
##     23), ])
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -5.9983 -2.0342 -0.2959  1.3315  6.0570 
## 
## Coefficients:
##               Estimate Std. Error t value Pr(>|t|)    
## (Intercept) -6.298e-01  2.632e+01  -0.024  0.98112    
## x1           1.596e-02  9.624e-03   1.658  0.11088    
## x2          -6.014e-01  2.693e-01  -2.233  0.03557 *  
## x3          -1.061e-01  5.835e-02  -1.818  0.08210 .  
## x4           1.881e-01  1.616e-01   1.164  0.25631    
## x5          -7.026e-05  3.860e-05  -1.820  0.08179 .  
## x6           7.676e-01  2.307e-01   3.328  0.00293 ** 
## x7           8.662e+00  1.374e+00   6.305 1.96e-06 ***
## x8          -3.105e-03  2.375e-03  -1.307  0.20403    
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 3.292 on 23 degrees of freedom
## Multiple R-squared:  0.769,  Adjusted R-squared:  0.6887 
## F-statistic: 9.571 on 8 and 23 DF,  p-value: 9.58e-06
anova(fwd.model)
## Analysis of Variance Table
## 
## Response: (y)
##           Df Sum Sq Mean Sq F value    Pr(>F)    
## x1         1   0.36    0.36  0.0336  0.856138    
## x2         1  65.08   65.08  6.0039  0.022302 *  
## x3         1  62.45   62.45  5.7614  0.024870 *  
## x4         1  87.54   87.54  8.0761  0.009236 ** 
## x5         1   9.52    9.52  0.8779  0.358506    
## x6         1 145.82  145.82 13.4519  0.001279 ** 
## x7         1 440.67  440.67 40.6528 1.661e-06 ***
## x8         1  18.53   18.53  1.7090  0.204029    
## Residuals 23 249.31   10.84                      
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#sintaks lain untuk mencari pemodelan terbaik
olsrr::ols_step_all_possible(model_tanpa_11_23)
##     Index N              Predictors     R-Square Adj. R-Square Mallow's Cp
## 7       1 1                      x7 0.4922477873  0.4753227135   22.555123
## 6       2 1                      x6 0.1839733368  0.1567724480   53.248938
## 3       3 1                      x3 0.0626628750  0.0314183041   65.327399
## 2       4 1                      x2 0.0603690794  0.0290480487   65.555784
## 8       5 1                      x8 0.0241353159 -0.0083935069   69.163454
## 5       6 1                      x5 0.0190427984 -0.0136557750   69.670498
## 1       7 1                      x1 0.0003376008 -0.0329844792   71.532910
## 4       8 1                      x4 0.0001095233 -0.0332201592   71.555619
## 20      9 2                   x2 x7 0.5737438368  0.5443468600   16.440844
## 34     10 2                   x6 x7 0.5581486176  0.5276761084   17.993606
## 29     11 2                   x4 x7 0.5460095109  0.5146998220   19.202255
## 14     12 2                   x1 x7 0.5070379531  0.4730405705   23.082517
## 32     13 2                   x5 x7 0.5026842532  0.4683866154   23.516000
## 36     14 2                   x7 x8 0.4936931393  0.4587754248   24.411214
## 25     15 2                   x3 x7 0.4922562404  0.4572394294   24.554281
## 19     16 2                   x2 x6 0.2180050148  0.1640743261   51.860522
## 28     17 2                   x4 x6 0.2095942986  0.1550835605   52.697948
## 35     18 2                   x6 x8 0.2030697701  0.1481090646   53.347572
## 13     19 2                   x1 x6 0.1968669341  0.1414784467   53.965167
## 24     20 2                   x3 x6 0.1861134735  0.1299833683   55.035852
## 31     21 2                   x5 x6 0.1852762906  0.1290884486   55.119207
## 16     22 2                   x2 x3 0.1065442228  0.0449265830   62.958286
## 17     23 2                   x2 x4 0.0903755207  0.0276427980   64.568147
## 26     24 2                   x3 x8 0.0853372155  0.0222570234   65.069794
## 22     25 2                   x3 x4 0.0811567280  0.0177882265   65.486030
## 10     26 2                   x1 x3 0.0786256802  0.0150826236   65.738038
## 23     27 2                   x3 x5 0.0718924802  0.0078850650   66.408439
## 21     28 2                   x2 x8 0.0695615126  0.0053933411   66.640526
## 18     29 2                   x2 x5 0.0681729042  0.0039089666   66.778784
## 9      30 2                   x1 x2 0.0606375598 -0.0041460567   67.529052
## 33     31 2                   x5 x8 0.0361538820 -0.0303182641   69.966807
## 30     32 2                   x4 x8 0.0266981870 -0.0404260760   70.908278
## 15     33 2                   x1 x8 0.0243583566 -0.0429272740   71.141247
## 27     34 2                   x4 x5 0.0217767039 -0.0456869717   71.398293
## 12     35 2                   x1 x5 0.0200354318 -0.0475483315   71.571665
## 11     36 2                   x1 x4 0.0005969036 -0.0683274479   73.507092
## 86     37 3                x4 x6 x7 0.6564433611  0.6196337213   10.206740
## 70     38 3                x2 x6 x7 0.6353603322  0.5962917964   12.305904
## 41     39 3                x1 x2 x7 0.6002558764  0.5574261489   15.801133
## 89     40 3                x5 x6 x7 0.5992191952  0.5562783947   15.904351
## 50     41 3                x1 x4 x7 0.5908809805  0.5470467998   16.734558
## 65     42 3                x2 x4 x7 0.5850499760  0.5405910448   17.315131
## 68     43 3                x2 x5 x7 0.5849556767  0.5404866421   17.324520
## 72     44 3                x2 x7 x8 0.5828414299  0.5381458689   17.535029
## 61     45 3                x2 x3 x7 0.5750767040  0.5295492081   18.308135
## 80     46 3                x3 x6 x7 0.5748023949  0.5292455087   18.335447
## 92     47 3                x6 x7 x8 0.5596568565  0.5124772340   19.843436
## 55     48 3                x1 x6 x7 0.5593242573  0.5121089992   19.876552
## 75     49 3                x3 x4 x7 0.5543971285  0.5066539637   20.367129
## 88     50 3                x4 x7 x8 0.5538933783  0.5060962402   20.417285
## 84     51 3                x4 x5 x7 0.5490546487  0.5007390753   20.899061
## 46     52 3                x1 x3 x7 0.5163791121  0.4645625884   24.152451
## 53     53 3                x1 x5 x7 0.5163163788  0.4644931337   24.158697
## 57     54 3                x1 x7 x8 0.5080778154  0.4553718670   24.978982
## 91     55 3                x5 x7 x8 0.5056059587  0.4526351686   25.225096
## 78     56 3                x3 x5 x7 0.5026947498  0.4494120444   25.514955
## 82     57 3                x3 x7 x8 0.4936945709  0.4394475607   26.411071
## 64     58 3                x2 x4 x6 0.3115701429  0.2378098011   44.544568
## 87     59 3                x4 x6 x8 0.2433947044  0.1623298513   51.332559
## 40     60 3                x1 x2 x6 0.2293883265  0.1468227901   52.727125
## 71     61 3                x2 x6 x8 0.2269847531  0.1441616910   52.966441
## 67     62 3                x2 x5 x6 0.2226051053  0.1393127952   53.402507
## 74     63 3                x3 x4 x6 0.2212821681  0.1378481147   53.534227
## 60     64 3                x2 x3 x6 0.2188301091  0.1351333351   53.778370
## 49     65 3                x1 x4 x6 0.2166301079  0.1326976195   53.997417
## 56     66 3                x1 x6 x8 0.2163040968  0.1323366787   54.029877
## 83     67 3                x4 x5 x6 0.2096483096  0.1249677713   54.692570
## 45     68 3                x1 x3 x6 0.2081988701  0.1233630348   54.836886
## 90     69 3                x5 x6 x8 0.2072357012  0.1222966691   54.932785
## 81     70 3                x3 x6 x8 0.2052177394  0.1200624972   55.133707
## 52     71 3                x1 x5 x6 0.2011627965  0.1155730961   55.537443
## 58     72 3                x2 x3 x4 0.1943817978  0.1080655619   56.212604
## 77     73 3                x3 x5 x6 0.1873270694  0.1002549697   56.915018
## 76     74 3                x3 x4 x8 0.1188226794  0.0244108236   63.735762
## 37     75 3                x1 x2 x3 0.1185019983  0.0240557838   63.767692
## 62     76 3                x2 x3 x8 0.1166367036  0.0219906361   63.953412
## 59     77 3                x2 x3 x5 0.1098664658  0.0144950157   64.627501
## 63     78 3                x2 x4 x5 0.1066643074  0.0109497689   64.946329
## 66     79 3                x2 x4 x8 0.1048333964  0.0089226889   65.128627
## 47     80 3                x1 x3 x8 0.1018566356  0.0056269894   65.425012
## 73     81 3                x3 x4 x5 0.0986484563  0.0020750766   65.744440
## 38     82 3                x1 x2 x4 0.0961676090 -0.0006715757   65.991449
## 43     83 3                x1 x3 x4 0.0951291552 -0.0018212925   66.094844
## 79     84 3                x3 x5 x8 0.0899440635 -0.0075619298   66.611106
## 44     85 3                x1 x3 x5 0.0836073137 -0.0145776170   67.242034
## 69     86 3                x2 x5 x8 0.0751444142 -0.0239472557   68.084655
## 42     87 3                x1 x2 x8 0.0697687458 -0.0298988886   68.619892
## 39     88 3                x1 x2 x5 0.0688063144 -0.0309644376   68.715718
## 85     89 3                x4 x5 x8 0.0426695700 -0.0599015475   71.318063
## 54     90 3                x1 x5 x8 0.0368341580 -0.0663621822   71.899074
## 51     91 3                x1 x4 x8 0.0276051276 -0.0765800373   72.817977
## 48     92 3                x1 x4 x5 0.0243324529 -0.0802033557   73.143826
## 158    93 4             x4 x5 x6 x7 0.6834395098  0.6365416594    9.518827
## 144    94 4             x2 x5 x6 x7 0.6767534021  0.6288650172   10.184540
## 141    95 4             x2 x4 x6 x7 0.6749077226  0.6267459038   10.368308
## 121    96 4             x1 x4 x6 x7 0.6714688202  0.6227975342   10.710707
## 161    97 4             x4 x6 x7 x8 0.6686233027  0.6195304587   10.994026
## 135    98 4             x2 x3 x6 x7 0.6616684631  0.6115452725   11.686495
## 151    99 4             x3 x4 x6 x7 0.6578092868  0.6071143663   12.070740
## 147   100 4             x2 x6 x7 x8 0.6443293726  0.5916374278   13.412888
## 105   101 4             x1 x2 x6 x7 0.6416958668  0.5886137729   13.675097
## 96    102 4             x1 x2 x3 x7 0.6329176547  0.5785350850   14.549113
## 100   103 4             x1 x2 x4 x7 0.6274777156  0.5722892291   15.090749
## 154   104 4             x3 x5 x6 x7 0.6222664170  0.5663058862   15.609620
## 103   105 4             x1 x2 x5 x7 0.6099089512  0.5521176847   16.840010
## 107   106 4             x1 x2 x7 x8 0.6087061153  0.5507366509   16.959772
## 162   107 4             x5 x6 x7 x8 0.6044887986  0.5458945466   17.379675
## 123   108 4             x1 x4 x7 x8 0.5997351815  0.5404366899   17.852976
## 124   109 4             x1 x5 x6 x7 0.5992405627  0.5398687942   17.902224
## 146   110 4             x2 x5 x7 x8 0.5978019617  0.5382170671   18.045460
## 143   111 4             x2 x4 x7 x8 0.5973159855  0.5376590945   18.093847
## 139   112 4             x2 x4 x5 x7 0.5918280644  0.5313581480   18.640261
## 110   113 4             x1 x3 x4 x7 0.5917865810  0.5313105189   18.644391
## 119   114 4             x1 x4 x5 x7 0.5916715533  0.5311784501   18.655844
## 115   115 4             x1 x3 x6 x7 0.5900289099  0.5292924521   18.819396
## 133   116 4             x2 x3 x5 x7 0.5858745916  0.5245226792   19.233027
## 130   117 4             x2 x3 x4 x7 0.5854279043  0.5240098161   19.277502
## 137   118 4             x2 x3 x7 x8 0.5840202201  0.5223935860   19.417661
## 157   119 4             x3 x6 x7 x8 0.5758654102  0.5130306562   20.229607
## 153   120 4             x3 x4 x7 x8 0.5648780095  0.5004154924   21.323584
## 127   121 4             x1 x6 x7 x8 0.5607005869  0.4956191924   21.739515
## 160   122 4             x4 x5 x7 x8 0.5581898740  0.4927365220   21.989498
## 149   123 4             x3 x4 x5 x7 0.5572407696  0.4916468095   22.083997
## 113   124 4             x1 x3 x5 x7 0.5237638542  0.4532103512   25.417177
## 126   125 4             x1 x5 x7 x8 0.5185828108  0.4472617458   25.933036
## 117   126 4             x1 x3 x7 x8 0.5169234055  0.4453565026   26.098257
## 156   127 4             x3 x5 x7 x8 0.5056445606  0.4324067178   27.221252
## 129   128 4             x2 x3 x4 x6 0.3324823526  0.2335908493   44.462412
## 142   129 4             x2 x4 x6 x8 0.3308702602  0.2317399284   44.622922
## 138   130 4             x2 x4 x5 x6 0.3127638333  0.2109510679   46.425716
## 99    131 4             x1 x2 x4 x6 0.3124480998  0.2105885591   46.457152
## 152   132 4             x3 x4 x6 x8 0.2593166036  0.1495857301   51.747271
## 122   133 4             x1 x4 x6 x8 0.2492616437  0.1380411465   52.748408
## 159   134 4             x4 x5 x6 x8 0.2447728171  0.1328873085   53.195345
## 109   135 4             x1 x3 x4 x6 0.2405517211  0.1280408650   53.615625
## 106   136 4             x1 x2 x6 x8 0.2387996962  0.1260292809   53.790068
## 102   137 4             x1 x2 x5 x6 0.2386355307  0.1258407945   53.806413
## 95    138 4             x1 x2 x3 x6 0.2365482817  0.1234443234   54.014233
## 145   139 4             x2 x5 x6 x8 0.2340915852  0.1206236719   54.258838
## 136   140 4             x2 x3 x6 x8 0.2279562759  0.1135794279   54.869710
## 116   141 4             x1 x3 x6 x8 0.2278118055  0.1134135544   54.884094
## 125   142 4             x1 x5 x6 x8 0.2255662892  0.1108353691   55.107672
## 132   143 4             x2 x3 x5 x6 0.2232678568  0.1081964282   55.336519
## 148   144 4             x3 x4 x5 x6 0.2212922345  0.1059281211   55.533225
## 118   145 4             x1 x4 x5 x6 0.2177098017  0.1018149576   55.889915
## 131   146 4             x2 x3 x4 x8 0.2167818303  0.1007495088   55.982310
## 112   147 4             x1 x3 x5 x6 0.2138792466  0.0974169127   56.271310
## 155   148 4             x3 x5 x6 x8 0.2092213049  0.0920689056   56.735086
## 128   149 4             x2 x3 x4 x5 0.2060438906  0.0884207633   57.051450
## 93    150 4             x1 x2 x3 x4 0.1996145750  0.0810389565   57.691594
## 111   151 4             x1 x3 x4 x8 0.1326975265  0.0042082712   64.354292
## 150   152 4             x3 x4 x5 x8 0.1300357498  0.0011521571   64.619316
## 97    153 4             x1 x2 x3 x8 0.1294366856  0.0004643427   64.678963
## 94    154 4             x1 x2 x3 x5 0.1198082355 -0.0105905445   65.637634
## 134   155 4             x2 x3 x5 x8 0.1184435644 -0.0121573890   65.773510
## 140   156 4             x2 x4 x5 x8 0.1176717857 -0.0130435053   65.850353
## 98    157 4             x1 x2 x4 x5 0.1167778479 -0.0140698783   65.939359
## 101   158 4             x1 x2 x4 x8 0.1110742179 -0.0206184906   66.507250
## 108   159 4             x1 x3 x4 x5 0.1066487639 -0.0256995673   66.947877
## 114   160 4             x1 x3 x5 x8 0.1034851078 -0.0293319133   67.262871
## 104   161 4             x1 x2 x5 x8 0.0756355473 -0.0613073346   70.035755
## 120   162 4             x1 x4 x5 x8 0.0455973582 -0.0957956258   73.026553
## 204   163 5          x2 x3 x5 x6 x7 0.7111564356  0.6556095963    8.759150
## 208   164 5          x2 x4 x5 x6 x7 0.7057887296  0.6492096392    9.293593
## 170   165 5          x1 x2 x3 x6 x7 0.7053365569  0.6486705101    9.338615
## 218   166 5          x4 x5 x6 x7 x8 0.7015080623  0.6441057665    9.719805
## 212   167 5          x2 x5 x6 x7 x8 0.6937017732  0.6347982680   10.497050
## 193   168 5          x1 x4 x5 x6 x7 0.6908810502  0.6314350983   10.777899
## 176   169 5          x1 x2 x4 x6 x7 0.6908351735  0.6313803992   10.782467
## 211   170 5          x2 x4 x6 x7 x8 0.6903338373  0.6307826522   10.832383
## 213   171 5          x3 x4 x5 x6 x7 0.6874109533  0.6272976750   11.123405
## 186   172 5          x1 x3 x4 x6 x7 0.6843241877  0.6236173007   11.430743
## 196   173 5          x1 x4 x6 x7 x8 0.6838391308  0.6230389636   11.479039
## 201   174 5          x2 x3 x4 x6 x7 0.6823934939  0.6213153197   11.622976
## 179   175 5          x1 x2 x5 x6 x7 0.6784330627  0.6165932671   12.017302
## 207   176 5          x2 x3 x6 x7 x8 0.6698380687  0.6063453896   12.873076
## 216   177 5          x3 x4 x6 x7 x8 0.6691798138  0.6055605473   12.938616
## 182   178 5          x1 x2 x6 x7 x8 0.6503431404  0.5831014366   14.814118
## 165   179 5          x1 x2 x3 x4 x7 0.6427116533  0.5740023558   15.573959
## 178   180 5          x1 x2 x4 x7 x8 0.6407649221  0.5716812533   15.767788
## 172   181 5          x1 x2 x3 x7 x8 0.6398899227  0.5706379848   15.854908
## 168   182 5          x1 x2 x3 x5 x7 0.6389870717  0.5695615086   15.944802
## 174   183 5          x1 x2 x4 x5 x7 0.6305240468  0.5594709789   16.787436
## 189   184 5          x1 x3 x5 x6 x7 0.6303374632  0.5592485138   16.806014
## 217   185 5          x3 x5 x6 x7 x8 0.6268646684  0.5551078738   17.151788
## 181   186 5          x1 x2 x5 x7 x8 0.6217413354  0.5489992845   17.661900
## 210   187 5          x2 x4 x5 x7 x8 0.6067939444  0.5311773953   19.150160
## 197   188 5          x1 x5 x6 x7 x8 0.6046074799  0.5285704568   19.367859
## 195   189 5          x1 x4 x5 x7 x8 0.6012317066  0.5245454963   19.703973
## 188   190 5          x1 x3 x4 x7 x8 0.6000006342  0.5230776792   19.826546
## 206   191 5          x2 x3 x5 x7 x8 0.5985113613  0.5213020077   19.974828
## 203   192 5          x2 x3 x4 x7 x8 0.5982971045  0.5210465477   19.996161
## 184   193 5          x1 x3 x4 x5 x7 0.5924796586  0.5141103621   20.575384
## 199   194 5          x2 x3 x4 x5 x7 0.5920023261  0.5135412350   20.622910
## 192   195 5          x1 x3 x6 x7 x8 0.5904783933  0.5117242381   20.774643
## 215   196 5          x3 x4 x5 x7 x8 0.5691055820  0.4862412708   22.902659
## 191   197 5          x1 x3 x5 x7 x8 0.5252169415  0.4339125072   27.272499
## 202   198 5          x2 x3 x4 x6 x8 0.3552922881  0.2313100358   44.191306
## 164   199 5          x1 x2 x3 x4 x6 0.3411982585  0.2145056159   45.594599
## 209   200 5          x2 x4 x5 x6 x8 0.3339947697  0.2059168408   46.311825
## 198   201 5          x2 x3 x4 x5 x6 0.3329585746  0.2046813774   46.414996
## 177   202 5          x1 x2 x4 x6 x8 0.3316257417  0.2030922305   46.547701
## 173   203 5          x1 x2 x4 x5 x6 0.3144327524  0.1825928971   48.259547
## 187   204 5          x1 x3 x4 x6 x8 0.2784782556  0.1397240740   51.839412
## 214   205 5          x3 x4 x5 x6 x8 0.2600286907  0.1177265158   53.676371
## 194   206 5          x1 x4 x5 x6 x8 0.2530452187  0.1094000685   54.371691
## 180   207 5          x1 x2 x5 x6 x8 0.2519272418  0.1080670960   54.483004
## 167   208 5          x1 x2 x3 x5 x6 0.2470333506  0.1022320718   54.970272
## 171   209 5          x1 x2 x3 x6 x8 0.2466253029  0.1017455534   55.010899
## 183   210 5          x1 x3 x4 x5 x6 0.2418507106  0.0960527703   55.486289
## 190   211 5          x1 x3 x5 x6 x8 0.2391834007  0.0928725162   55.751864
## 205   212 5          x2 x3 x5 x6 x8 0.2348622485  0.0877203732   56.182106
## 200   213 5          x2 x3 x4 x5 x8 0.2246811634  0.0755813871   57.195801
## 166   214 5          x1 x2 x3 x4 x8 0.2223913793  0.0728512599   57.423787
## 163   215 5          x1 x2 x3 x4 x5 0.2084320593  0.0562074553   58.813668
## 185   216 5          x1 x3 x4 x5 x8 0.1391107989 -0.0264448167   65.715745
## 169   217 5          x1 x2 x3 x5 x8 0.1297959692 -0.0375509598   66.643190
## 175   218 5          x1 x2 x4 x5 x8 0.1278113731 -0.0399172090   66.840789
## 225   219 6       x1 x2 x3 x5 x6 x7 0.7419392960  0.6800047270    7.694207
## 245   220 6       x2 x4 x5 x6 x7 x8 0.7288261044  0.6637443695    8.999842
## 244   221 6       x2 x3 x5 x6 x7 x8 0.7276762521  0.6623185526    9.114329
## 222   222 6       x1 x2 x3 x4 x6 x7 0.7244550367  0.6583242456    9.435054
## 240   223 6       x2 x3 x4 x5 x6 x7 0.7207857922  0.6537743823    9.800388
## 229   224 6       x1 x2 x4 x5 x6 x7 0.7134319670  0.6446556391   10.532583
## 228   225 6       x1 x2 x3 x6 x7 x8 0.7119046910  0.6427618168   10.684648
## 239   226 6       x1 x4 x5 x6 x7 x8 0.7083485104  0.6383521528   11.038725
## 232   227 6       x1 x2 x4 x6 x7 x8 0.7065653375  0.6361410185   11.216269
## 234   228 6       x1 x3 x4 x5 x6 x7 0.7051572038  0.6343949327   11.356472
## 246   229 6       x3 x4 x5 x6 x7 x8 0.7039440081  0.6328905700   11.477266
## 243   230 6       x2 x3 x4 x6 x7 x8 0.6959422542  0.6229683952   12.273973
## 233   231 6       x1 x2 x5 x6 x7 x8 0.6948433998  0.6216058157   12.383382
## 237   232 6       x1 x3 x4 x6 x7 x8 0.6936424517  0.6201166401   12.502956
## 224   233 6       x1 x2 x3 x4 x7 x8 0.6530788592  0.5698177855   16.541732
## 227   234 6       x1 x2 x3 x5 x7 x8 0.6485197708  0.5641645158   16.995664
## 220   235 6       x1 x2 x3 x4 x5 x7 0.6457277406  0.5607023983   17.273657
## 231   236 6       x1 x2 x4 x5 x7 x8 0.6457152152  0.5606868669   17.274904
## 238   237 6       x1 x3 x5 x6 x7 x8 0.6336246726  0.5456945940   18.478718
## 242   238 6       x2 x3 x4 x5 x7 x8 0.6074282616  0.5132110444   21.087003
## 236   239 6       x1 x3 x4 x5 x7 x8 0.6014082073  0.5057461771   21.686399
## 223   240 6       x1 x2 x3 x4 x6 x8 0.3645044249  0.2119854869   45.274085
## 241   241 6       x2 x3 x4 x5 x6 x8 0.3572178468  0.2029501300   45.999584
## 219   242 6       x1 x2 x3 x4 x5 x6 0.3435362469  0.1859849462   47.361814
## 230   243 6       x1 x2 x4 x5 x6 x8 0.3360074186  0.1766491991   48.111433
## 235   244 6       x1 x3 x4 x5 x6 x8 0.2830259345  0.1109521588   53.386615
## 226   245 6       x1 x2 x3 x5 x6 x8 0.2614861058  0.0842427712   55.531261
## 221   246 6       x1 x2 x3 x4 x5 x8 0.2277794890  0.0424465664   58.887312
## 251   247 7    x1 x2 x3 x5 x6 x7 x8 0.7553878988  0.6840427027    8.355177
## 247   248 7    x1 x2 x3 x4 x5 x6 x7 0.7518338690  0.6794520808    8.709039
## 254   249 7    x2 x3 x4 x5 x6 x7 x8 0.7413872746  0.6659585631    9.749170
## 252   250 7    x1 x2 x4 x5 x6 x7 x8 0.7357998678  0.6587414958   10.305489
## 250   251 7    x1 x2 x3 x4 x6 x7 x8 0.7357290625  0.6586500391   10.312539
## 253   252 7    x1 x3 x4 x5 x6 x7 x8 0.7189184505  0.6369363319   11.986313
## 249   253 7    x1 x2 x3 x4 x5 x7 x8 0.6577692031  0.5579518873   18.074731
## 248   254 7    x1 x2 x3 x4 x5 x6 x8 0.3697742025  0.1859583449   46.749392
## 255   255 8 x1 x2 x3 x4 x5 x6 x7 x8 0.7689986635  0.6886503725    9.000000
olsrr::ols_step_forward_p(model_tanpa_11_23)
## 
##                             Selection Summary                             
## -------------------------------------------------------------------------
##         Variable                  Adj.                                       
## Step    Entered     R-Square    R-Square     C(p)        AIC        RMSE     
## -------------------------------------------------------------------------
##    1    x7            0.4922      0.4753    22.5551    187.7097    4.2740    
##    2    x2            0.5737      0.5443    16.4408    184.1112    3.9829    
##    3    x6            0.6354      0.5963    12.3059    181.1150    3.7490    
##    4    x5            0.6768      0.6289    10.1845    179.2592    3.5946    
##    5    x3            0.7112      0.6556     8.7591    177.6582    3.4627    
##    6    x1            0.7419      0.6800     7.6942    176.0521    3.3378    
##    7    x8            0.7554      0.6840     8.3552    176.3395    3.3167    
##    8    x4            0.7690      0.6887     9.0000    176.5074    3.2924    
## -------------------------------------------------------------------------
olsrr::ols_step_backward_p(model_tanpa_11_23)
## [1] "No variables have been removed from the model."
olsrr::ols_step_both_p(model_tanpa_11_23)
## 
##                              Stepwise Selection Summary                               
## -------------------------------------------------------------------------------------
##                      Added/                   Adj.                                       
## Step    Variable    Removed     R-Square    R-Square     C(p)        AIC        RMSE     
## -------------------------------------------------------------------------------------
##    1       x7       addition       0.492       0.475    22.5550    187.7097    4.2740    
##    2       x2       addition       0.574       0.544    16.4410    184.1112    3.9829    
##    3       x6       addition       0.635       0.596    12.3060    181.1150    3.7490    
##    4       x5       addition       0.677       0.629    10.1850    179.2592    3.5946    
##    5       x3       addition       0.711       0.656     8.7590    177.6582    3.4627    
##    6       x1       addition       0.742       0.680     7.6940    176.0521    3.3378    
## -------------------------------------------------------------------------------------

##Uji asumsi model terbaik##

#uji kehomogenan ragam stepwise
library(ggplot2)
library(dplyr)
data.frame(rstandard(step.model),
           step.model$fitted.values) %>%
  ggplot(aes(x = step.model$fitted.values, y = rstandard(step.model))) + 
  geom_point() +
  geom_hline(yintercept = 0, linetype = "dotted") +
  labs(title = "Standardized Residuals vs Fitted Values Plot")

plot(step.model,1)

library(lmtest)
bptest(step.model)
## 
##  studentized Breusch-Pagan test
## 
## data:  step.model
## BP = 4.0201, df = 6, p-value = 0.674
#uji kehomogenan ragam backward
library(ggplot2)
library(dplyr)
data.frame(rstandard(back.model),
           back.model$fitted.values) %>%
  ggplot(aes(x = back.model$fitted.values, y = rstandard(back.model))) + 
  geom_point() +
  geom_hline(yintercept = 0, linetype = "dotted") +
  labs(title = "Standardized Residuals vs Fitted Values Plot")

plot(back.model,1)

library(lmtest)
bptest(back.model)
## 
##  studentized Breusch-Pagan test
## 
## data:  back.model
## BP = 4.0201, df = 6, p-value = 0.674
#nilai harapan = nol stepwise
t.test(resid(step.model), mu = 0,) 
## 
##  One Sample t-test
## 
## data:  resid(step.model)
## t = -3.2411e-16, df = 31, p-value = 1
## alternative hypothesis: true mean is not equal to 0
## 95 percent confidence interval:
##  -1.080683  1.080683
## sample estimates:
##     mean of x 
## -1.717376e-16
#h0: nilai harapan sisaan=0

#nilai harapan = nol backwared
t.test(resid(back.model), mu = 0,) 
## 
##  One Sample t-test
## 
## data:  resid(back.model)
## t = -3.2411e-16, df = 31, p-value = 1
## alternative hypothesis: true mean is not equal to 0
## 95 percent confidence interval:
##  -1.080683  1.080683
## sample estimates:
##     mean of x 
## -1.717376e-16
#h0: nilai harapan sisaan=0

#cek autokorelasi stepwise dan backward
sisaan1 <- step.model$residuals
sisaan2 <- back.model$residuals
plot(x=1:dim(data[-c(11,23),])[1],
     y=sisaan1,type='b',
     ylab="Sisaan",xlab="Urutan")

plot(x=1:dim(data[-c(11,23),])[1],
     y=sisaan2,type='b',
     ylab="Sisaan",xlab="Urutan")

# Uji kenormalan stepwise
plot(step.model,2)
shapiro.test(residuals(step.model)) 
## 
##  Shapiro-Wilk normality test
## 
## data:  residuals(step.model)
## W = 0.96202, p-value = 0.3116
#ho: sisaan menyebar normal

# Uji kenormalan stepwise
plot(back.model,2)

shapiro.test(residuals(back.model)) 
## 
##  Shapiro-Wilk normality test
## 
## data:  residuals(back.model)
## W = 0.96202, p-value = 0.3116
#ho: sisaan menyebar normal