如何使用dplyr根据与列名称匹配的字符串选择R中的列？
R中的列选择通常使用列号或其名称和$delta运算符完成。我们还可以选择带有部分名称字符串或完整名称的列，而无需使用$delta运算符。这可以通过dplyr软件包的selectandmatch功能来完成。
示例
加载dplyr软件包-
> library(dplyr)
考虑以R为底的BOD数据-
> str(BOD) 'data.frame': 6 obs. of 2 variables: $ Time : num 1 2 3 4 5 7 $ demand: num 8.3 10.3 19 16 15.6 19.8 - attr(*, "reference")= chr "A1.4, p. 270"
选择具有字符串“and”的BOD数据列-
> select(BOD,matches("and"))
demand
1 8.3
2 10.3
3 19.0
4 16.0
5 15.6
6 19.8考虑以R为底的树数据
> str(trees) 'data.frame': 31 obs. of 3 variables: $ Girth : num 8.3 8.6 8.8 10.5 10.7 10.8 11 11 11.1 11.2 ... $ Height: num 70 65 63 72 81 83 66 75 80 75 ... $ Volume: num 10.3 10.3 10.2 16.4 18.8 19.7 15.6 18.2 22.6 19.9 ...
选择具有字符串“Vol”的列-
> select(trees,matches("Vol"))
Volume
1 10.3
2 10.3
3 10.2
4 16.4
5 18.8
6 19.7
7 15.6
8 18.2
9 22.6
10 19.9
11 24.2
12 21.0
13 21.4
14 21.3
15 19.1
16 22.2
17 33.8
18 27.4
19 25.7
20 24.9
21 34.5
22 31.7
23 36.3
24 38.3
25 42.6
26 55.4
27 55.7
28 58.3
29 51.5
30 51.0
31 77.0考虑基数R中的女性数据-
> str(women) 'data.frame': 15 obs. of 2 variables: $ height: num 58 59 60 61 62 63 64 65 66 67 ... $ weight: num 115 117 120 123 126 129 132 135 139 142 ...
选择具有字符串“string”的列-
> select(women,matches("height"))
height
1 58
2 59
3 60
4 61
5 62
6 63
7 64
8 65
9 66
10 67
11 68
12 69
13 70
14 71
15 72考虑基数R中的mtcars数据-
> str(mtcars) 'data.frame': 32 obs. of 11 variables: $ mpg : num 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ... $ cyl : num 6 6 4 6 8 6 8 4 4 6 ... $ disp: num 160 160 108 258 360 ... $ hp : num 110 110 93 110 175 105 245 62 95 123 ... $ drat: num 3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ... $ wt : num 2.62 2.88 2.32 3.21 3.44 ... $ qsec: num 16.5 17 18.6 19.4 17 ... $ vs : num 0 0 1 1 0 1 0 1 1 1 ... $ am : num 1 1 1 0 0 0 0 0 0 0 ... $ gear: num 4 4 4 3 3 3 3 4 4 4 ... $ carb: num 4 4 1 1 2 1 4 2 2 4 ...
选择具有字符串“mpg”的列-
> select(mtcars,matches("mpg"))
mpg
Mazda RX4 21.0
Mazda RX4 Wag 21.0
Datsun 710 22.8
Hornet 4 Drive 21.4
Hornet Sportabout 18.7
Valiant 18.1
Duster 360 14.3
Merc 240D 24.4
Merc 230 22.8
Merc 280 19.2
Merc 280C 17.8
Merc 450SE 16.4
Merc 450SL 17.3
Merc 450SLC 15.2
Cadillac Fleetwood 10.4
Lincoln Continental 10.4
Chrysler Imperial 14.7
Fiat 128 32.4
Honda Civic 30.4
Toyota Corolla 33.9
Toyota Corona 21.5
Dodge Challenger 15.5
AMC Javelin 15.2
Camaro Z28 13.3
Pontiac Firebird 19.2
Fiat X1-9 27.3
Porsche 914-2 26.0
Lotus Europa 30.4
Ford Pantera L 15.8
Ferrari Dino 19.7
Maserati Bora 15.0
Volvo 142E 21.4考虑以R为底的睡眠数据
> str(sleep) 'data.frame': 20 obs. of 3 variables: $ extra: num 0.7 -1.6 -0.2 -1.2 -0.1 3.4 3.7 0.8 0 2 ... $ group: Factor w/ 2 levels "1","2": 1 1 1 1 1 1 1 1 1 1 ... $ ID : Factor w/ 10 levels "1","2","3","4",..: 1 2 3 4 5 6 7 8 9 10 ...
选择具有字符串“ext”的列-
> select(sleep,matches("ext"))
extra
1 0.7
2 -1.6
3 -0.2
4 -1.2
5 -0.1
6 3.4
7 3.7
8 0.8
9 0.0
10 2.0
11 1.9
12 0.8
13 1.1
14 0.1
15 -0.1
16 4.4
17 5.5
18 1.6
19 4.6
20 3.4