My favorite tool for answering questions like this is www.r-project.org -> search -> "R site search". When I asked there for "subsetting by NA" just now, I got 101 hits, the third of which mentioned "is.na". Also, the posting guide "R-project.org/posting-guide.html" gives other useful tips for how to find information about R.
hope this helps. spencer graves
Benjamin M. Osborne wrote:
I want to know where all the NAs are in a matrix. The data frame looks like this:
vmc[1:5,]date year month day snow.new prcp tmin snow.dep tmax
1 01NOV1954 1954 11 1 NA NA -14.44444 NA 12.2222222
2 02NOV1954 1954 11 2 NA NA -13.88889 NA 2.2222222
3 03NOV1954 1954 11 3 NA NA -16.66667 NA -1.1111111
4 04NOV1954 1954 11 4 NA NA NA NA -0.5555556
5 05NOV1954 1954 11 5 NA NA -17.22222 NA -2.7777778
tmean yearmo
1 -1.111111 195411
2 -5.833333 195411
3 -8.888889 195411
4 NA 195411
5 -10.000000 195411
This does not work:
subset(vmc, snow.new==NA)
[1] date year month day snow.new prcp tmin snow.dep [9] tmax tmean yearmo <0 rows> (or 0-length row.names)
Because:
NA==NA
[1] NA
How can I return all rows of this data frame that contain NA in a particular field?
Thanks, Ben Osborne
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