导入数据：
grades<-read.table("D:/ProgramData/test1.txt",sep=" ")
求均值：mean（）
求方差：sd（）
保存数据：write.table(grades,"D:/ProgramData/test2.txt")
> grades<-read.table("D:/ProgramData/test1.txt",sep=" ")
> grades
V1 V2 V3 V4 V5 V6 V7
1 编号 1.00 2.0 3.00 4.0 5.00 6.00
2 身高m 1.75 1.8 1.65 1.9 1.74 1.91
3 体重kg 60.00 72.0 57.00 90.0 95.00 72.00
> data1<-as.matrix(grades)
> data1
V1 V2 V3 V4 V5 V6 V7
[1,] "编号" " 1.00" " 2.0" " 3.00" " 4.0" " 5.00" " 6.00"
[2,] "身高m" " 1.75" " 1.8" " 1.65" " 1.9" " 1.74" " 1.91"
[3,] "体重kg" "60.00" "72.0" "57.00" "90.0" "95.00" "72.00"
> data2<-as.numeric(data1[2,2:7])
> data2
[1] 1.75 1.80 1.65 1.90 1.74 1.91
> mean1=mean(data2)
> mean1
[1] 1.791667
> data3<-as.numeric(data1[3,2:7])
> data3
[1] 60 72 57 90 95 72
> mean2=mean(data3)
> mean2
[1] 74.33333
> grades[1,8]="mean"
> grades[2,8]=mean1
> grades[3,8]=mean2
> grades
V1 V2 V3 V4 V5 V6 V7 V8
1 编号 1.00 2.0 3.00 4.0 5.00 6.00 mean
2 身高m 1.75 1.8 1.65 1.9 1.74 1.91 1.79166666666667
3 体重kg 60.00 72.0 57.00 90.0 95.00 72.00 74.3333333333333
> sd1=sd(data2)
> sd2=sd(data3)
> grades[1,9]="sd"
> grades[2,9]=sd1
> grades[3,9]=sd2
> grades
V1 V2 V3 V4 V5 V6 V7 V8
1 编号 1.00 2.0 3.00 4.0 5.00 6.00 mean
2 身高m 1.75 1.8 1.65 1.9 1.74 1.91 1.79166666666667
3 体重kg 60.00 72.0 57.00 90.0 95.00 72.00 74.3333333333333
V9
1 sd
2 0.100282933077701
3 15.4229266569827
> write.table(grades,"D:/ProgramData/test2.txt")
