rcross-correlation

From cross correlation to column format in R

I have the following cross-correlation matrix:

df =

   A B C
A  1 7 1
B  7 1 9
C  1 9 1

and I would like to make it into the following format:

A B 7
A C 1
B C 9

any straightforward R code that can do such thing?

Solution

  • Not a straightforward way but an option in base R :

    mat[upper.tri(mat, diag = TRUE)] <- NA
tmp <- which(!is.na(mat), arr.ind = TRUE)
data.frame(col = colnames(mat)[tmp[, 2]], row = rownames(tmp), val = mat[tmp])

#  col row val
#1   A   B   7
#2   A   C   1
#3   B   C   9

    data

    mat <- structure(c(1L, 7L, 1L, 7L, 1L, 9L, 1L, 9L, 1L), .Dim = c(3L, 
3L), .Dimnames = list(c("A", "B", "C"), c("A", "B", "C")))