此刻只是自学R并且有点陷入困境。我有一个数据集，我想总结（找到平均值，最大值等），但只选择那些对某个变量有特定值的情况。
或者，我想可以通过仅汇总数据集中的某些行来完成相同的结果（即仅汇总第1行到第20行）。
有人可以伸出援助之手吗？非常感谢
答案 0 :(得分：4)
mydata<-mtcars
一个。查找第1行到第20行的摘要
summary(mydata[1:20,])
mpg cyl disp hp drat wt qsec vs am
Min. :10.40 Min. :4.0 Min. : 71.1 Min. : 52.0 Min. :2.760 Min. :1.615 Min. :15.84 Min. :0.0 Min. :0.0
1st Qu.:16.10 1st Qu.:4.0 1st Qu.:145.2 1st Qu.: 94.5 1st Qu.:3.070 1st Qu.:2.811 1st Qu.:17.41 1st Qu.:0.0 1st Qu.:0.0
Median :18.95 Median :6.0 Median :196.3 Median :116.5 Median :3.460 Median :3.440 Median :18.15 Median :0.5 Median :0.0
Mean :20.13 Mean :6.2 Mean :233.9 Mean :136.2 Mean :3.545 Mean :3.398 Mean :18.44 Mean :0.5 Mean :0.3
3rd Qu.:22.80 3rd Qu.:8.0 3rd Qu.:296.9 3rd Qu.:180.0 3rd Qu.:3.920 3rd Qu.:3.743 3rd Qu.:19.45 3rd Qu.:1.0 3rd Qu.:1.0
Max. :33.90 Max. :8.0 Max. :472.0 Max. :245.0 Max. :4.930 Max. :5.424 Max. :22.90 Max. :1.0 Max. :1.0
gear carb
Min. :3.0 Min. :1.00
1st Qu.:3.0 1st Qu.:1.75
Median :3.5 Median :3.00
Mean :3.5 Mean :2.70
3rd Qu.:4.0 3rd Qu.:4.00
Max. :4.0 Max. :4.00
湾当cyl = 4
的值时查找摘要summary(mydata[mydata$cyl==4,])
mpg cyl disp hp drat wt qsec vs am
Min. :21.40 Min. :4 Min. : 71.10 Min. : 52.00 Min. :3.690 Min. :1.513 Min. :16.70 Min. :0.0000 Min. :0.0000
1st Qu.:22.80 1st Qu.:4 1st Qu.: 78.85 1st Qu.: 65.50 1st Qu.:3.810 1st Qu.:1.885 1st Qu.:18.56 1st Qu.:1.0000 1st Qu.:0.5000
Median :26.00 Median :4 Median :108.00 Median : 91.00 Median :4.080 Median :2.200 Median :18.90 Median :1.0000 Median :1.0000
Mean :26.66 Mean :4 Mean :105.14 Mean : 82.64 Mean :4.071 Mean :2.286 Mean :19.14 Mean :0.9091 Mean :0.7273
3rd Qu.:30.40 3rd Qu.:4 3rd Qu.:120.65 3rd Qu.: 96.00 3rd Qu.:4.165 3rd Qu.:2.623 3rd Qu.:19.95 3rd Qu.:1.0000 3rd Qu.:1.0000
Max. :33.90 Max. :4 Max. :146.70 Max. :113.00 Max. :4.930 Max. :3.190 Max. :22.90 Max. :1.0000 Max. :1.0000
gear carb
Min. :3.000 Min. :1.000
1st Qu.:4.000 1st Qu.:1.000
Median :4.000 Median :2.000
Mean :4.091 Mean :1.545
3rd Qu.:4.000 3rd Qu.:2.000
Max. :5.000 Max. :2.000