[R] Extracting dataframe rows containing NAs in one column

[kaallen]

Hi,

I am working on a data set which looks like this:

> head(temp)
  Day Month Year   PW  ROW
1   1     1 1959   NA 6.40
2   2     1 1959 6.65 6.35
3   3     1 1959 2.50 3.60
4   4     1 1959 0.60 2.25
5   5     1 1959 0.85 0.30
6   6     1 1959 0.00 2.20

I am trying to extract all the rows containing NA. I can extrat all the rows
without NAs in column 4 using 

> PWna<-temp[complete.cases(temp[,4]),]
> head(PWna)
  Day Month Year   PW  ROW
2   2     1 1959 6.65 6.35
3   3     1 1959 2.50 3.60
4   4     1 1959 0.60 2.25
5   5     1 1959 0.85 0.30
6   6     1 1959 0.00 2.20
7   7     1 1959 1.40 1.65

But can't figure out how to extract the rows WITH the NAs. Can anyone advise
me?

Thanks in advance

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