Question

在R.中我有一个子集，例如mtcars，并希望对一些连续的行进行子集，指定我想要选择的行的名字和姓氏。我怎么能这样做？

为了说明，我有

                         mpg cyl  disp  hp drat    wt  qsec vs am gear carb
Mazda RX4              R   6 160.0 110 3.90 2.620 16.46  0  1    4    4
Mazda RX4 Wag          R   6 160.0 110 3.90 2.875 17.02  0  1    4    4
Datsun 710          22.8   4 108.0  93 3.85 2.320 18.61  1  1    4    1
Hornet 4 Drive      21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1
Hornet Sportabout   18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2
Valiant             18.1   6 225.0 105 2.76 3.460 20.22  1  0    3    1
Duster 360          14.3   8 360.0 245 3.21 3.570 15.84  0  0    3    4
Merc 240D           24.4   4 146.7  62 3.69 3.190 20.00  1  0    4    2
Merc 230            22.8   4 140.8  95 3.92 3.150 22.90  1  0    4    2
Merc 280            19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4
Merc 280C           17.8   6 167.6 123 3.92 3.440 18.90  1  0    4    4
Merc 450SE          16.4   8 275.8 180 3.07 4.070 17.40  0  0    3    3
Merc 450SL          17.3   8 275.8 180 3.07 3.730 17.60  0  0    3    3
Merc 450SLC         15.2   8 275.8 180 3.07 3.780 18.00  0  0    3    3
Cadillac Fleetwood  10.4   8 472.0 205 2.93 5.250 17.98  0  0    3    4
Lincoln Continental 10.4   8 460.0 215 3.00 5.424 17.82  0  0    3    4
Chrysler Imperial   14.7   8 440.0 230 3.23 5.345 17.42  0  0    3    4
Fiat 128            32.4   4  78.7  66 4.08 2.200 19.47  1  1    4    1
Honda Civic         30.4   4  75.7  52 4.93 1.615 18.52  1  1    4    2
Toyota Corolla      33.9   4  71.1  65 4.22 1.835 19.90  1  1    4    1
Toyota Corona       21.5   4 120.1  97 3.70 2.465 20.01  1  0    3    1
Dodge Challenger    15.5   8 318.0 150 2.76 3.520 16.87  0  0    3    2
AMC Javelin         15.2   8 304.0 150 3.15 3.435 17.30  0  0    3    2
Camaro Z28          13.3   8 350.0 245 3.73 3.840 15.41  0  0    3    4
Pontiac Firebird    19.2   8 400.0 175 3.08 3.845 17.05  0  0    3    2
Fiat X1-9           27.3   4  79.0  66 4.08 1.935 18.90  1  1    4    1
Porsche 914-2         26   4 120.3  91 4.43 2.140 16.70  0  1    5    2
Lotus Europa        30.4   4  95.1 113 3.77 1.513 16.90  1  1    5    2
Ford Pantera L      15.8   8 351.0 264 4.22 3.170 14.50  0  1    5    4
Ferrari Dino        19.7   6 145.0 175 3.62 2.770 15.50  0  1    5    6
Maserati Bora         15   8 301.0 335 3.54 3.570 14.60  0  1    5    8
Volvo 142E          21.4   4 121.0 109 4.11 2.780 18.60  1  1    4    2

我喜欢选择前5行，正如我对mtcars[1:5,]所做的那样，但是使用了行的名称。看似mtcars["Mazda RX4":"Hornet Sportabout",]的东西，虽然这段代码不起作用。

Answer 1

使用which提取行号。

mtcars[which(rownames(mtcars) == "Mazda RX4"):which(rownames(mtcars) == "Hornet Sportabout"),]

Answer 2

另一种方法是使用dplyr，但是Josh的slution更优雅，因为dplyr does not deal with row names

require(dplyr)
mtcars$names<-rownames(mtcars)
selection<-filter(mtcars, names==c("Mazda RX4", "Mazda RX4 Wag", "Datsun 710", "Hornet 4 Drive", "Hornet Sportabout"))

selection
   mpg cyl disp  hp drat    wt  qsec vs am gear carb             names
1 21.0   6  160 110 3.90 2.620 16.46  0  1    4    4         Mazda RX4
2 21.0   6  160 110 3.90 2.875 17.02  0  1    4    4     Mazda RX4 Wag
3 22.8   4  108  93 3.85 2.320 18.61  1  1    4    1        Datsun 710
4 21.4   6  258 110 3.08 3.215 19.44  1  0    3    1    Hornet 4 Drive
5 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2 Hornet Sportabout

Answer 3

你应该创建一个你想要的项目向量，但它不适用于“：”

mtcars[c("Mazda RX4","Mazda RX4 Wag","Datsun 710","Hornet 4 Drive","Hornet Sportabout"),]

如何根据有序名称对R中的行进行子集化

3 个答案: