Find names of columns which contain missing values

Question

I want to find all the names of columns with `NA` or missing data and store these column names in a vector. ``` # create matrix a <- c(1,2,3,4,5,NA,7,8,9,10,NA,12,13,14,NA,16,17,18,19,20) cnames <- c("aa", "bb", "cc", "dd", "ee") mymatrix <- matrix(a, nrow = 4, ncol = 5, byrow = TRUE) colnames(mymatrix) <- cnames mymatrix # aa bb cc dd ee # [1,] 1 2 3 4 5 # [2,] NA 7 8 9 10 # [3,] NA 12 13 14 NA # [4,] 16 17 18 19 20 ``` The desired result: columns `"aa"` and `"ee"`. My attempt: ``` bad <- character() for (j in 1:4){ tmp <- which(colnames(mymatrix[j, ]) %in% c("", "NA")) bad <- tmp } ``` However, I keep getting `integer(0)` as my output. Any help is appreciated.

Accepted Answer

Like this?

```
colnames(mymatrix)[colSums(is.na(mymatrix)) > 0]
# [1] "aa" "ee"
```

Or as suggested by @thelatemail:

```
names(which(colSums(is.na(mymatrix)) > 0))
# [1] "aa" "ee"
```

Find names of columns which contain missing values

Solution

Problem