r - Determine the number of NA values in a column -


i want count number of na values in data frame column. data frame called df, , name of column considering col. way have come following: 

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

is good/most efficient way this?

you're over-thinking problem:

sum(is.na(df$col))

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