convert a matrix to a list
mat2list(x)
a list that contains matrix columns as its elements
x <- matrix(1:15, nrow = 3)
mat2list(x)
#> [[1]]
#> [1] 1 2 3
#>
#> [[2]]
#> [1] 4 5 6
#>
#> [[3]]
#> [1] 7 8 9
#>
#> [[4]]
#> [1] 10 11 12
#>
#> [[5]]
#> [1] 13 14 15
#>