R-table和tapply函數
(2013-03-15 09:49:23)table可統計數據的頻數
tapply可根據因子、向量和要計算的函數計算
> class<-c(1,2,3,2,1,2,1,3)
> class
[1] 1 2 3
> c(81,65,72,88,73,91,56,90)->student
> class
[1] 1 2 3 2 1 2 1 3
>factor(class)->class
> tapply(student,class,mean)
1 2 3
70.00000 81.33333 81.00000
> tapply(student,class,min)
1 2 3
56 65 72
> tapply(student,class,max)
1 2 3
81 91 90
> table(class)
class
1 2 3
3 3 2
>