用R中的列中位数进行插补 [英] Imputation with column medians in R

问题描述

例如，如果我有矢量

vec <- c(3,4,5,NA)

我可以使用以下代码将NA替换为向量中其他值的中值:

I can replace the NA with the median value of the other values in the vector with the following code:

vec[which(is.na(vec))] <- median(vec, na.rm = T)

但是，如果我有一个包含NA的矩阵，则在矩阵的所有列上应用相同的代码并不会给我返回矩阵，而只是返回每个矩阵列的中位数.

However, if I have a matrix containing NAs, applying this same code across all columns of the matrix doesn't give me back a matrix, just returning the medians of each matrix column.

mat <- matrix(c(1,NA,3,5,6,7,NA,3,4,NA,2,8), ncol = 3)
apply(mat, 2, function(x) x[which(is.na(x))] <- median(x, na.rm=T) )

#[1] 3 6 4

如何用NA中位数代替列中位数来取回矩阵?这个问题类似:按行均值替换NA值，但我不能根据我的情况调整任何解决方案.

How can I get the matrix back with NAs replaced by column medians? This question is similar: Replace NA values by row means but I can't adapt any of the solutions to my case.

推荐答案

将return(x)添加为apply中函数的最后一行即可解决该问题.

Adding return(x) as last line of the function within apply will solve it.

> apply(mat, 2, function(x){
    x[which(is.na(x))] <- median(x, na.rm=T)
    return(x)
  })
     [,1] [,2] [,3]
[1,]    1    6    4
[2,]    3    7    4
[3,]    3    6    2
[4,]    5    3    8

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