Say I have a sparse matrix M1
i<-c(1,5,2,4,2,2,8)
j<-c(2,5,3,2,4,2,4)
x<-rpois(7,2)
M1<-sparseMatrix(i,j,x=x)
rownames(M1) <- c("a", "b", "c", "d", "e", "f", "g", "h")
colnames(M1) <- c("L1", "L2", "L3", "L4", "L5")
M1
where M1 looks like:
8 x 5 sparse Matrix of class "dgCMatrix"
L1 L2 L3 L4 L5
a . 3 . . .
b . 1 3 0 .
c . . . . .
d . 4 . . .
e . . . . 1
f . . . . .
g . . . . .
h . . . 0 .
how would i make a set of interacting row-col pairs in a list that looks something like:
(a, L2)
(b, L2)
(b, L3)
(b, L4)
(d, L2)
(e, L5)
(h, L4)
Thanks!
Use which with arr.ind = TRUE on a logical matrix and extract the row names and column names based on the row/col index
i1 <- which(M1 > 0, arr.ind = TRUE)
library(dplyr)
tibble(rn = row.names(M1)[i1[,1]], cn = colnames(M1)[i1[,2]]) %>%
arrange(rn)
-ouptut
# A tibble: 7 x 2
rn cn
<chr> <chr>
1 a L2
2 b L2
3 b L3
4 b L4
5 d L2
6 e L5
7 h L4