在数据框中随机采样一定百分比的行 [英] Randomly sample a percentage of rows within a data frame

问题描述

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gender <- c("F", "M", "M", "F", "F", "M", "F", "F")
age    <- c(23, 25, 27, 29, 31, 33, 35, 37)
mydf <- data.frame(gender, age) 

mydf[ sample( which(mydf$gender=='F'), 3 ), ]

代替选择行数(在上述情况下为3)，我如何随机选择20％带有"F"的行?因此，在带有"F"的五行中，如何随机采样其中的20％.

Instead of selecting a number of rows (3 in above case), how can I randomly select 20% of rows with "F"? So of the five rows with "F", how do I randomly sample 20% of those rows.

推荐答案

这是怎么回事:

mydf[ sample( which(mydf$gender=='F'), round(0.2*length(which(mydf$gender=='F')))), ]

其中0.2是您的20％，length(which(mydf$gender=='F'))是具有F的行总数

Where 0.2 is your 20% and length(which(mydf$gender=='F')) is the total number of rows with F

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