Counting non NAs in a data frame; getting answer as a vector

Question

Say I have the following R data.frame ZZZ:

( ZZZ <- structure(list(n = c(1, 2, NA), m = c(6, NA, NA), o = c(7, 8, 
8)), .Names = c(\         


        

Answer 1

Try this:

# define "demo" dataset
ZZZ <- data.frame(n=c(1,2,NA),m=c(6,NA,NA),o=c(7,8,8))
# apply the counting function per columns
apply(ZZZ, 2, function(x) length(which(!is.na(x))))

Having run:

> apply(ZZZ, 2, function(x) length(which(!is.na(x))))
n m o 
2 1 3 

If you really insist on returning a vector, you might use as.vector, e.g. by defining this function:

nonNAs <- function(x) {
    as.vector(apply(x, 2, function(x) length(which(!is.na(x)))))
    }

You could simply run nonNAs(ZZZ):

> nonNAs(ZZZ)
[1] 2 1 3