Question

How can I turn the following matrix (or table/data frame) with row names & column names,

    A       B
M   27143   18324
F   29522   18875

into something like

27143  M  A
18324  M  B
29522  F  A
18875  F  B

so that I can do some analysis in R?

Answer 1

You can use the reshape2 package and melt the data.

temp = read.table(header=TRUE, text="    A       B
M   27143   18324
F   29522   18875")
library(reshape2)
temp$id = rownames(temp)
melt(temp)
# Using id as id variables
# id variable value
# 1  M        A 27143
# 2  F        A 29522
# 3  M        B 18324
# 4  F        B 18875