R/corner.R

In LieberInstitute/jaffelab: Commonly used functions by the Jaffe lab

#' corner, an improved head()
#'
#' Returns the first part of an object similar to head() but subsets
#' columns as well as rows, and also handles lists of objects.
#'
#' @param mat A DataFrame, data.frame, GRanges, matrix, tibble, or list
#' @param n Integer number of rows and columns you want returned
#'
#' @return An n x n object of the original class (or a list of n nxn objects)
#' @export
#' @author Emily E. Burke
#'
#' @examples
#'
#' m <- matrix(rnorm(1000), ncol = 10)
#' corner(m)
#'
#' lis <- list(iris, mtcars, matrix(rnorm(1000), ncol = 10))
#' corner(lis)
corner <- function(mat, n = 6) {
    types <-
        c(
            "list",
            "DataFrame",
            "data.frame",
            "GRanges",
            "matrix",
            "tbl_df"
        )
    if (!any(vapply(types, function(y, x) is(x, y), logical(1), mat))) {
        stop(
            "The class of your object (",
            class(mat),
            ") is not handled by this function.",
            call. = FALSE
        )
    }
    if (is(mat[1], "list")) {
        # return corners of first n items of list
        return(lapply(mat[seq_len(min(length(mat), n))], function(x) {
            x[seq_len(min(nrow(x), n)), seq_len(min(ncol(x), n))]
        }))
    } else {
        return(mat[seq_len(min(nrow(mat), n)), seq_len(min(ncol(mat), n))])
    }
}