podatki <- read.table("./Avtomobili.csv", header = TRUE, sep = ";", dec = ",", encoding = "UTF-8")

head(podatki)
##       znamka       tip sedezi  ccm  kw  km vrtljajimax navor vrtljajinav  Motor dolzina sirina visina medosna teza_kg
## 1 Alfa Romeo  1642,0TS      5 1995 107 146        5800   187        5000 Bencin     455    176    139     266    1380
## 2 Alfa Romeo spyder2,0      2 1969 110 150        6200   187        4000 Bencin     429    178    132     254    1370
## 3 Alfa Romeo  1552,0TS      5 1969 110 150        6200   187        4000 Bencin     444    173    143     254    1300
## 4 Alfa Romeo    GTV2,0      2 1969 110 150        6200   187        4000 Bencin     429    178    132     254    1370
## 5 Alfa Romeo      1452      5 1969 110 150        6200   187        4000 Bencin     410    171    143     254    1240
## 6 Alfa Romeo  1551,8TS      5 1747 103 140        6300   165        4000 Bencin     445    173    144     254    1270
##   tezadov_kg pospesek hitrost poraba_120  cena poraba_90 pogon
## 1       1805      9.9     210        8.3 50170       6.5     1
## 2       1630      8.4     210        7.8 56390       6.2     1
## 3       1840      9.0     210        8.0 38390       6.2     1
## 4       1780      8.4     215        7.8 54290       6.2     1
## 5       1760      8.4     210        8.0 28750       6.2     1
## 6       1795     10.0     205        8.2 30490       6.1     1

Opis izbrane kategorialne spremenljivke:

LM model

fit <- lm(poraba_90 ~ km + pogon, 
          data = podatki)

summary(fit)
## 
## Call:
## lm(formula = poraba_90 ~ km + pogon, data = podatki)
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -3.3534 -0.6259 -0.1377  0.5679  5.4287 
## 
## Coefficients:
##              Estimate Std. Error t value Pr(>|t|)    
## (Intercept) 3.2495515  0.1348049   24.11   <2e-16 ***
## km          0.0161795  0.0008047   20.11   <2e-16 ***
## pogon       0.8746889  0.0714071   12.25   <2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 1.098 on 462 degrees of freedom
## Multiple R-squared:  0.6334, Adjusted R-squared:  0.6318 
## F-statistic: 399.2 on 2 and 462 DF,  p-value: < 2.2e-16

Ustvarjanje umetnih spremenljivk

podatki$pogonF <- factor(podatki$pogon, 
                         levels = c(1, 2, 3), 
                         labels = c("Pogon spredaj", "Pogon zadaj", "4X4"))

head(podatki)
##       znamka       tip sedezi  ccm  kw  km vrtljajimax navor vrtljajinav  Motor dolzina sirina visina medosna teza_kg
## 1 Alfa Romeo  1642,0TS      5 1995 107 146        5800   187        5000 Bencin     455    176    139     266    1380
## 2 Alfa Romeo spyder2,0      2 1969 110 150        6200   187        4000 Bencin     429    178    132     254    1370
## 3 Alfa Romeo  1552,0TS      5 1969 110 150        6200   187        4000 Bencin     444    173    143     254    1300
## 4 Alfa Romeo    GTV2,0      2 1969 110 150        6200   187        4000 Bencin     429    178    132     254    1370
## 5 Alfa Romeo      1452      5 1969 110 150        6200   187        4000 Bencin     410    171    143     254    1240
## 6 Alfa Romeo  1551,8TS      5 1747 103 140        6300   165        4000 Bencin     445    173    144     254    1270
##   tezadov_kg pospesek hitrost poraba_120  cena poraba_90 pogon        pogonF
## 1       1805      9.9     210        8.3 50170       6.5     1 Pogon spredaj
## 2       1630      8.4     210        7.8 56390       6.2     1 Pogon spredaj
## 3       1840      9.0     210        8.0 38390       6.2     1 Pogon spredaj
## 4       1780      8.4     215        7.8 54290       6.2     1 Pogon spredaj
## 5       1760      8.4     210        8.0 28750       6.2     1 Pogon spredaj
## 6       1795     10.0     205        8.2 30490       6.1     1 Pogon spredaj
fit <- lm(poraba_90 ~ km + pogonF, 
          data = podatki)

summary(fit)
## 
## Call:
## lm(formula = poraba_90 ~ km + pogonF, data = podatki)
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -3.5445 -0.5608 -0.1389  0.5362  5.3812 
## 
## Coefficients:
##                    Estimate Std. Error t value Pr(>|t|)    
## (Intercept)       3.9297190  0.1165673  33.712   <2e-16 ***
## km                0.0185355  0.0009052  20.477   <2e-16 ***
## pogonFPogon zadaj 0.1384895  0.1579833   0.877    0.381    
## pogonF4X4         1.8758834  0.1410910  13.296   <2e-16 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
## 
## Residual standard error: 1.068 on 461 degrees of freedom
## Multiple R-squared:  0.6537, Adjusted R-squared:  0.6514 
## F-statistic:   290 on 3 and 461 DF,  p-value: < 2.2e-16