Determine the number of NA values in a column

I want to count the number of NA values in a data frame column. Say my data frame is called df, and the name of the column I am considering is col. The way I have come up with is following:

sapply(df$col, function(x) sum(length(which(is.na(x)))))  

Is this a good/most efficient way to do this?

Solution 1:

You're over-thinking the problem:

sum(is.na(df$col))

Solution 2:

If you are looking for NA counts for each column in a dataframe then:

na_count <-sapply(x, function(y) sum(length(which(is.na(y)))))

should give you a list with the counts for each column.

na_count <- data.frame(na_count)

Should output the data nicely in a dataframe like:

----------------------
| row.names | na_count
------------------------
| column_1  | count