[R] How to count the number of NAs in each column of a df?

[Chuck Cleland]

Richard M. Heiberger wrote:
> drop.col.kna <- function(mydf, k)
>  mydf[sapply(mydf, function(x) sum(is.na(x))) < k]
> 
> tmp <- data.frame(matrix(1:24, 6,4, dimnames=list(letters[1:6], LETTERS[1:4])))
> tmp[1:3,1] <- NA
> tmp[2:5,2] <- NA
> tmp[6,3] <- NA
> 
> drop.col.kna(tmp, 0)
> drop.col.kna(tmp, 1)
> drop.col.kna(tmp, 2)
> drop.col.kna(tmp, 3)
> drop.col.kna(tmp, 4)
> drop.col.kna(tmp, 5)
> drop.col.kna(tmp, 6)

  Possibly simpler (does not require a new function definition and seems
highly intuitive) might be something like this:

tmp.dropna <- tmp[,colSums(is.na(tmp)) < 2]

tmp.dropna
   C  D
a 13 19
b 14 20
c 15 21
d 16 22
e 17 23
f NA 24

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-- 
Chuck Cleland, Ph.D.
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