Question

I want to find frequency of a matrix by their column. for example for matrix x below

   x <- matrix(c(rep(1:4,3),rep(2:5,2)),4,5)
   x
         [,1] [,2] [,3] [,4] [,5]
   [1,]    1    1    1    2    2
   [2,]    2    2    2    3    3
   [3,]    3    3    3    4    4
   [4,]    4    4    4    5    5

now how can find frequency of each unique column and create a matrix that each column is a unique column of x and the last row is added as the frequency of it in matrix x

 #freqmatrix
        [,1] [,2]
 [,1]      1  2
 [,2]      2  3
 [,3]      3  4
 [,4]      4  5
 [,5]      3  2

Answer 1

What’s your end goal, exactly? In other words, how are you going to work with this data further? If it’s just tabulation, doesn’t paste() get you to the answer?

x <- matrix(c(rep(1:4,3),rep(2:5,2)),4,5)
x1 <- data.frame(table(apply(x, 2, paste, collapse = ", ")))
#         Var1 Freq
# 1 1, 2, 3, 4    3
# 2 2, 3, 4, 5    2

If you do want Var1 separated, you can use read.csv() on that column.

cbind(read.csv(text = as.character(x1$Var1), header = FALSE), x1[-1])
#   V1 V2 V3 V4 Freq
# 1  1  2  3  4    3
# 2  2  3  4  5    2

Or, if you prefer to transpose your output:

t(cbind(read.csv(text = as.character(x1$Var1), header = FALSE), x1[-1]))
#      [,1] [,2]
# V1      1    2
# V2      2    3
# V3      3    4
# V4      4    5
# Freq    3    2