Converting an object of class "table" to matrix in R

Question

I am having a hard time converting from an object of class "table" to a matrix:

I have a categorical variable (a factor in R) and I am using its counts. I have this counts stored in a table:

my.table = table(my.dataframef$cat.variable)
class(my.table)
[1] "table"

After using this table to do some barplots I want to do a segmented barplot and so I need this information in the form of a matrix. This is what I am doing, but it wont work (elements are not in the correct order):

my.matrix = matrix(my.table, nrow = n.matrix.rows, ncol = n.matrix.cols)

I have solved my problem for a 2x2 matrix by mannually assigning each element to its position:

my.matrix = matrix (c(my.table[4],my.table[3],my.table[2],my.table[1]),
        nrow=2,ncol=2)

I was wondering if there is an "automatic way" to do this as with bigger matrix it becomes a tough exercise...

Thank you for your help, I appreciate it!

Answer 1

Well, that's not hard if you know that a table is an array with the extra class "table" attached: You just unclass() :

> tab <- structure(c(686L, 337L, 686L, 466L), .Dim = c(2L, 2L), 
             .Dimnames = list( c("male(mnt)", "female(mnt)"), 
                               c("male(auth)", "female(auth)" )))
> tab
            male(auth) female(auth)
male(mnt)          686          686
female(mnt)        337          466
> (mat <- unclass(tab))
            male(auth) female(auth)
male(mnt)          686          686
female(mnt)        337          466
> class(mat)
[1] "matrix"
> 

Answer 2

This approach works for me:

tab <- table(sample(LETTERS, 1e4, replace = T), sample(letters, 1e4, replace = T))
class(tab) # table
mat <- matrix(as.numeric(tab), nrow = nrow(tab), ncol = ncol(tab))
class(mat) # matrix
all(mat == tab) # TRUE

Answer 3

> table(letters[1:3], 1:3)

    1 2 3
  a 1 0 0
  b 0 1 0
  c 0 0 1

> class(table(letters[1:3], 1:3))
[1] "table"                                    # is a table

> class(as.matrix(table(letters[1:3], 1:3)))   # still a table
[1] "table"

> as.data.frame(table(letters[1:3], 1:3))      # doesn't work
  Var1 Var2 Freq
1    a    1    1
2    b    1    0
3    c    1    0
4    a    2    0
5    b    2    1
6    c    2    0
7    a    3    0
8    b    3    0
9    c    3    1

> as.data.frame.matrix(table(letters[1:3], 1:3)) # works
  1 2 3
a 1 0 0
b 0 1 0
c 0 0 1

> class(as.matrix(as.data.frame.matrix(table(letters[1:3], 1:3)))) # to your goal
[1] "matrix"