R/subsample_matrix.R

In qenvio/hicutils:

#' Sub sample a HiC contact matrix
#'
#' This function takes a HiC contact matrix and returns a sub sample of it. The input matrix should be triangular.
#' @import magrittr
#' @import Matrix
#' @importFrom dplyr summarize
#' @importFrom dplyr slice
#' @param mat HiC contact map matrix
#' @param p Numeric probability of being sub-sampled
#' @return A sub-sampled HiC contact matrix
#' @export
#' @examples
#' plot(0)

subsample_matrix <- function(mat, p = .5){

    idx <- min(100, nrow(mat))
    
    check <- summary(mat[1:idx, 1:idx]) %>%
        summarize(upper = sum(i > j),
                  lower = sum(j > i)) %>%
        slice(1) %>%
        unlist

    if(!any(check  == 0)) stop("Matrix should be triangular")
    
    mat@x <- rbinom(length(mat@x), mat@x, prob = p) %>% as.numeric

    drop0(mat)

}