I have a regular matrix (non-sparse) that I would like to convert to a sparseMatrix (using the Matrix package). Is there a function to do this or do I need to do a bunch of loops?
ex.
> regMat <- matrix(0, nrow=10, ncol=10)
> regMat[3,5] <- round(runif(1),2)*100
> regMat[2,8] <- round(runif(1),2)*100
> regMat[8,4] <- round(runif(1),2)*100
> regMat[1,6] <- round(runif(1),2)*100
> regMat[7,4] <- round(runif(1),2)*100
> regMat
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 0 0 0 0 0 49 0 0 0 0
[2,] 0 0 0 0 0 0 0 93 0 0
[3,] 0 0 0 0 20 0 0 0 0 0
[4,] 0 0 0 0 0 0 0 0 0 0
[5,] 0 0 0 0 0 0 0 0 0 0
[6,] 0 0 0 0 0 0 0 0 0 0
[7,] 0 0 0 8 0 0 0 0 0 0
[8,] 0 0 0 14 0 0 0 0 0 0
[9,] 0 0 0 0 0 0 0 0 0 0
[10,] 0 0 0 0 0 0 0 0 0 0
Any suggestions?
Here are two options:
library(Matrix)
A <- as(regMat, "sparseMatrix") # see also `vignette("Intro2Matrix")`
B <- Matrix(regMat, sparse = TRUE) # Thanks to Aaron for pointing this out
identical(A, B)
# [1] TRUE
A
# 10 x 10 sparse Matrix of class "dgCMatrix"
#
# [1,] . . . . . 45 . . . .
# [2,] . . . . . . . 59 . .
# [3,] . . . . 95 . . . . .
# [4,] . . . . . . . . . .
# [5,] . . . . . . . . . .
# [6,] . . . . . . . . . .
# [7,] . . . 23 . . . . . .
# [8,] . . . 63 . . . . . .
# [9,] . . . . . . . . . .
# [10,] . . . . . . . . . .