# [R] "apply" question

From: Christoph Scherber <Christoph.Scherber_at_uni-jena.de>
Date: Tue 03 May 2005 - 00:52:48 EST

Iīve got a simple question but somehow I canīt find the solution:

I have a data frame with columns 1-5 containing one set of integer values, and columns 6-10 containing another set of integer values. Columns 6-10 contain NAīs at some places.

I now want to calculate
(1) the number of values in each row of columns 6-10 that were NAīs
(2) the sum of all values on columns 1-5 for which there were no missing
values in the corresponding cells of columns 6-10.

Example: (letīs call the data frame "data")

Col1 Col2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10

```1      2      5      2      3      NA      5      NA    1      4
3      1      4      5      2      6      NA      4     NA     1

```

The result would then be (for the first row)
(1) "There were 2 NAīs in columns 6-10."
(2) The mean of Columns 1-5 was 2+2+3=7" (because there were NAīs in the
1st and 3rd position in rows 6-10)

So far, I know how to calculate the rowSums for the data.frame, but I donīt know how to condition these on the values of columns 6-10

rowSums(data[,1:5]) #thatīs straightforward apply(data[,6:19],1,function(x)sum(is.na(x))) #this also works fine

But I donīt know how to select just the desired values of columns 1-5
(as described above)

Can anyone help me? Thanks a lot in advance!

Best regards
Christoph

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