R/draw.R

In Thie1e/convenience: A small collection of diverse functions for more convenient working in R

#' Randomly draw rows or elements from an object
#'
#' Randomly draw n rows/elements from an object. Can be useful as an alternative
#' to head(), tail() or ht(). May also be used to quickly draw random samples.
#' Works with tibbles, too, but will return a data.frame in that case.
#' @param x An object
#' @param n Single positive integer. The number of rows/elements to be randomly
#' drawn.
#' @param replace If TRUE draw with replacement. Default FALSE
#' @keywords sample
#' @export
#' @examples
#' set.seed(4321)
#' draw(iris, 6L)
#' ###      Sepal.Length Sepal.Width Petal.Length Petal.Width    Species
#' ###  51           7.0         3.2          4.7         1.4 versicolor
#' ###  136          7.7         3.0          6.1         2.3  virginica
#' ###  61           5.0         2.0          3.5         1.0 versicolor
#' ###  7            4.6         3.4          1.4         0.3     setosa
#' ###  112          6.4         2.7          5.3         1.9  virginica
#' ###  109          6.7         2.5          5.8         1.8  virginica

draw <- function(x, n = 10L, replace = F){
    stopifnot(n >= 0)
    dimension <- dim(x)
    if (is.null(dimension)){
        # Vector or list
        return(x[sample(seq_along(x), size = n, replace = replace)])
    } else if ("tbl_df" %in% class(x)) {
        return(data.frame(x)[sample(1:dimension[1], size = n, replace = replace), ])
    } else {
        # Matrix or data.frame
        return(x[sample(1:dimension[1], size = n, replace = replace), ])
    }
}