1

165個

library(MASS)
## 
## Attaching package: 'MASS'
## The following object is masked from 'package:dplyr':
## 
##     select
ls("package:MASS")[94:103]
##  [1] "minn38"            "motors"            "muscle"           
##  [4] "mvrnorm"           "nclass.freq"       "neg.bin"          
##  [7] "negative.binomial" "negexp.SSival"     "newcomb"          
## [10] "nlschools"

2

dta<-women
coef(lm(weight ~ height, data = dta))
## (Intercept)      height 
##   -87.51667     3.45000
dta<-women
dta$height_centered<-with(height-mean(height),data=dta)
coef(lm(weight ~ height_centered, data = dta))
##     (Intercept) height_centered 
##        136.7333          3.4500

每筆數據減掉平均(常數)，不會改變截距只會有平移的效果。

3

c(women) 
## $height
##  [1] 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72
## 
## $weight
##  [1] 115 117 120 123 126 129 132 135 139 142 146 150 154 159 164
c(as.matrix(women))
##  [1]  58  59  60  61  62  63  64  65  66  67  68  69  70  71  72 115 117
## [18] 120 123 126 129 132 135 139 142 146 150 154 159 164

c(women) 將高度及重量兩變項分為兩個表以list顯示。

c(as.matrix(women))將所有數值以一個矩陣呈現。

4

library(MASS)
head(birthwt)
##    low age lwt race smoke ptl ht ui ftv  bwt
## 85   0  19 182    2     0   0  0  1   0 2523
## 86   0  33 155    3     0   0  0  0   3 2551
## 87   0  20 105    1     1   0  0  0   1 2557
## 88   0  21 108    1     1   0  0  1   2 2594
## 89   0  18 107    1     1   0  0  1   0 2600
## 91   0  21 124    3     0   0  0  0   0 2622
c("White", "Black", "Other")[birthwt$race]
##   [1] "Black" "Other" "White" "White" "White" "Other" "White" "Other"
##   [9] "White" "White" "Other" "Other" "Other" "Other" "White" "White"
##  [17] "Black" "White" "Other" "White" "Other" "White" "White" "Other"
##  [25] "Other" "White" "White" "White" "Black" "Black" "Black" "White"
##  [33] "Black" "White" "Black" "White" "White" "White" "White" "White"
##  [41] "Black" "White" "Black" "White" "White" "White" "White" "Other"
##  [49] "White" "Other" "White" "Other" "White" "White" "Other" "Other"
##  [57] "Other" "Other" "Other" "Other" "Other" "Other" "Other" "White"
##  [65] "Other" "Other" "Other" "Other" "White" "Black" "White" "Other"
##  [73] "Other" "Black" "White" "Black" "White" "White" "Black" "White"
##  [81] "White" "White" "Other" "Other" "Other" "Other" "Other" "White"
##  [89] "White" "White" "White" "Other" "White" "White" "White" "White"
##  [97] "White" "White" "White" "White" "White" "White" "Other" "White"
## [105] "Other" "Black" "White" "White" "White" "Black" "White" "Other"
## [113] "White" "White" "White" "Other" "White" "Other" "White" "Other"
## [121] "White" "Other" "White" "White" "White" "White" "White" "White"
## [129] "White" "White" "Other" "White" "Black" "Other" "Other" "Other"
## [137] "Other" "Black" "Other" "White" "White" "White" "Other" "Other"
## [145] "White" "White" "Black" "White" "Other" "Other" "Other" "White"
## [153] "White" "White" "White" "Other" "Black" "White" "Black" "Other"
## [161] "White" "Other" "Other" "Other" "Black" "White" "Other" "Other"
## [169] "White" "White" "Black" "Black" "Black" "Other" "Other" "White"
## [177] "White" "White" "White" "Black" "Other" "Other" "White" "Other"
## [185] "White" "Other" "Other" "Black" "White"
?help
## starting httpd help server ... done

原數值應是以1,2,3呈現，而c(“White”, “Black”, “Other”)[birthwt$race]取代為“White”, “Black”, “Other”