r - 如何将数据框随机拆分为三个具有给定行数的较小数据框

Question

我想使用 R 将一个数据帧随机拆分为三个较小的数据帧。第一个占总观测值的 80%。第二个和第三个分别占总观测值的 15% 和 5%。三个数据框不能有任何重叠。你有什么建议吗？

Answer 1

这里有一个快速函数，可根据您在“props”参数中指定的值数量分成任意数量的组。它应该是相当 self 解释的

#' Splits data.frame into arbitrary number of groups
#' 
#' @param dat The data.frame to split into groups
#' @param props Numeric vector. What proportion of the data should
#'              go in each group?
#' @param which.adjust Numeric. Which group size should we 'fudge' to
#'              make sure that we sample enough (or not too much)
split_data <- function(dat, props = c(.8, .15, .05), which.adjust = 1){

    # Make sure proportions are positive
    # and the adjustment group isn't larger than the number
    # of groups specified
    stopifnot(all(props >= 0), which.adjust <= length(props))

    # could check to see if the sum is 1
    # but this is easier
    props <- props/sum(props)
    n <- nrow(dat)
    # How large should each group be?
    ns <- round(n * props)
    # The previous step might give something that
    # gives sum(ns) > n so let's force the group
    # specified in which.adjust to be a value that
    # makes it so that sum(ns) = n
    ns[which.adjust] <- n - sum(ns[-which.adjust])

    ids <- rep(1:length(props), ns)
    # Shuffle ids so that the groups are randomized
    which.group <- sample(ids)
    split(dat, which.group)
}

split_data(mtcars)
split_data(mtcars, c(.7, .3))