如何将随机“NA"添加到数据框中 [英] How do I add random `NA`s into a data frame

问题描述

我用随机值创建了一个数据框

I created a data frame with random values

n <- 50
df <- data.frame(id = seq (1:n),
age = sample(c(20:90), n, rep = TRUE), 
sex = sample(c("m", "f"), n, rep = TRUE, prob = c(0.55, 0.45))
)

并想介绍一些 NA 值来模拟真实世界的数据.我正在尝试使用 apply 但无法到达那里.线

and would like to introduce a few NA values to simulate real world data. I am trying to use apply but cannot get there. The line

apply(subset(df,select=-id), 2, function(x) {x[sample(c(1:n),floor(n/10))]})

可以检索随机值，但是

will retrieve random values alright, but

apply(subset(df,select=-id), 2, function(x) {x[sample(c(1:n),floor(n/10))]<-NA}) 

不会将它们设置为 NA.也尝试过 with 和 within.

will not set them to NA. Have tried with and within, too.

暴力破解:

for (i in (1:floor(n/10))) {
  df[sample(c(1:n), 1), sample(c(2:ncol(df)), 1)] <- NA
  }

但我更喜欢使用 apply 系列.

But I'd prefer to use the apply family.

推荐答案

在你的函数中返回 x:

> df <- apply (df, 2, function(x) {x[sample( c(1:n), floor(n/10))] <- NA; x} )
> tail(df)
      id   age  sex
[45,] "45" "41" NA 
[46,] "46" NA   "f"
[47,] "47" "38" "f"
[48,] "48" "32" "f"
[49,] "49" "53" NA 
[50,] "50" "74" "f"

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