Collapse matrix

Takes a two-dimensional matrix and collapses row or columns according to a specified function.

collapse_matrix(x, groups, dim = 1, FUN = sum)

Arguments

x	A matrix object.
groups	A vector or factor of the same length as the rows or columns of x, which indicates which elements to collapse.
dim	Which dimension to collapse. 1 for rows and 2 for columns
FUN	Function (or function name) to apply to elements per groups

Value

Returns a matrix object.

Details

This function uses plyr functions to aggregate columnwise or rowwise according to a grouping factor.

Examples

x <- cbind(rbind(matrix(0,2,2),matrix(1,2,2)),
           rbind(matrix(1,2,2),matrix(0,2,2)))
colnames(x) <- c("C1","C2","C3","C4")
row.names(x) <- c("R1","R2","R3","R4")

x
#>    C1 C2 C3 C4
#> R1  0  0  1  1
#> R2  0  0  1  1
#> R3  1  1  0  0
#> R4  1  1  0  0
collapse_matrix(x=x,groups = rep(c(1,2),each=2),dim=1,FUN=sum)
#>    X1
#>     C1 C2 C3 C4
#>   1  0  0  2  2
#>   2  2  2  0  0
collapse_matrix(x=x,groups = rep(c(1,2),each=2),dim=2,FUN=mean)
#>     
#> X1   1 2
#>   R1 0 1
#>   R2 0 1
#>   R3 1 0
#>   R4 1 0