🚀 go-pugleaf

I use the following function to convert lists to matrices.  

l2m <- function(...) do.call("cbind", ...)

If l is a list of equal length vectors, then 

m <- l2m(l) 

Will create a matric out of the vectors. This has the advantage that
it avoids an explicit loop over the elements of the list and also
maintains the list names as column names.  To join matrix elements
into a single matrix by rows, the cbind could be replaced by rbind.

Also, be aware that using apply for row and columns sums is horrible.
Since apply has an explicit loop in its definition it is very slow.
This applies to other uses of apply as well, but for row and column
sums there is a much more efficient solution available by using matrix
multiply.

rowsum <- function(x) c(x %*% rep(1, ncol(x)))

colsum <- function(x) c(rep(1, nrow(x)) %*% x)

David

----------David Lubinsky---------------------------------------------
Email: david@hoqax.att.com
                          
Phone: (908) 949-1722
Fax:   (908) 949-7724
Mail: AT&T Bell Laboratories, Room 2J524, Crawfords Corner Rd,
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D