如何将给定行数的数据帧随机分为三个较小的帧 [英] how to randomly split a data frame into three smaller ones with given numbers of rows

问题描述

使用R，我想将一个数据帧随机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％。这三个数据帧不能有任何重叠。您有任何建议吗？

Using R, I want to randomly split a data frame into three smaller data frames. The first one has 80% of the total observations. The second and the third have, respectively, 15% and 5% of the total observations. The three data frames cannot have any overlaps. Do you have any suggestions?

推荐答案

这是一个快速功能，可根据您有多少个值分为任意数量的组在 props参数中指定。应该是很自我解释的

Here is a quick function to split into an arbitrary number of groups depending on how many values you specify in the 'props' parameter. It should be fairly self explanatory

#' 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))

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