How to get frequencies then add it as a variable in an array?

Question

Let\'s say I have an array of this format

X  Y  Z
A  1  0
A  2  1
B  1  1
B  2  1
B  1  0

I want to find the frequency of X and the frequen

Answer 1

Using ave and assuming your data is dat

dat$Fx <-  with(dat,ave(Y,list(X),FUN=length))
dat$Fyx <- with(dat,ave(Y,list(X,Y),FUN=length))

Result:

  X Y Z Fx Fyx
1 A 1 0  2   1
2 A 2 1  2   1
3 B 1 1  3   2
4 B 2 1  3   1
5 B 1 0  3   2

If the data doesn't have a numeric column for ave to work on, then:

dat$Fx <-  with(dat,ave(seq_len(nrow(dat)),list(X),FUN=length))
dat$Fyx <- with(dat,ave(seq_len(nrow(dat)),list(X,Y),FUN=length))