#' Returns quickly indices for a matrix of size N
#'
#' This is used in conjunction with apply to get around
#' doing nested loops in R. This function is slightly
#' faster than expand.grid. This function was lifted
#' from a discussion on stackoverflow.
#' @param seq The first Sequence.
#' @param only.unique Makes sure to return only i,j and not
#' both [i,j] and [j,i] values
#' @return A matrix of indicies
#' @export
indices <- function( seq, only.unique=TRUE ) {
ret <- cbind( c(t(matrix(rep.int(seq, length(seq)), nrow=length(seq)))), rep.int(seq, length(seq)) )
if( only.unique)
ret <- ret[ ret[,1] < ret[,2], ]
return(ret)
}
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