Show columns with NAs in a data.frame

Question

I\'d like to show the names of columns in a large dataframe that contain missing values. Basically, I want the equivalent of complete.cases(df) but for columns, not rows. Some o

Answer 1

One way...

nacols <- function(x){
  y <- sapply(x, function(xx)any(is.na(xx)))
  names(y[y])
}  

nacols(tmp)
[1] "y" "z"

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Explanation: since the result y is a logical vector, names(y[y]) returns the names of y for only those cases where y is TRUE.