On 2010-12-08 12:10, Wade Wall wrote:
Hi all,
How can one evaluate NAs in a numeric dataframe column? For example, I have
a dataframe (demo) with a column of numbers and several NAs. If I write
demo.df>= 10, numerals will return TRUE or FALSE, but if the value is
"NA", "NA" is returned. But if I write demo.df == "NA", it returns as "NA"
also. I know that I can remove NAs, but would like to keep the dataframe as
is without creating a subset. I basically want to add a line that evaluates
the NA in the demo dataframe.
As an example, I want to assign rows to classes based on values in
demo$Area. Some of the values in demo$Area are "NA"
for (i in 1:nrow(demo)) {
if (demo$Area[i]> 0&& demo$Area[i]< 10) {Class[i]<-"S01"} ## 1-10 cm2
if (demo$Area[i]>= 10&& demo$Area[i]< 25) {Class[i]<- "S02"} ##
10-25cm2
if (demo$Area[i]>= 25&& demo$Area[i]< 50) {Class[i]<-"S03"} ## 25-50
cm2
if (demo$Area[i]>= 50&& demo$Area[i]< 100) {Class[i]<-"S04"} ## 50-100
cm2
if (demo$Area[i]>= 100&& demo$Area[i]< 200) {Class[i]<- "S05"} ##
100-200 cm2
if (demo$Area[i]>= 200&& demo$Area[i]< 400) {Class[i]<- "S06"} ##
200-400 cm2
if (demo$Area[i]>= 400&& demo$Area[i]< 800) {Class[i]<- "S07"} ##
400-800 cm2
if (demo$Area[i]>= 800&& demo$Area[i]< 1600) {Class[i]<- "S08"} ##
800-1600 cm2
if (demo$Area[i]>= 1600&& demo$Area[i]< 3200) {Class[i]<- "S09"} ##
1600-3200 cm2
if (demo$Area[i]>=3200) {Class[i]<- "S10"} ##>3200 cm2
}
What happens is that I get the message "Error in if (demo$Area[i]> 0&&
demo$Area[i]< 10) { : missing value where TRUE/FALSE needed"
You don't say what you want to have occur when x is NA. (I don't know
what 'evaluate NA' means.)
But why not just use something like:
for(....){
if(!is.na(x[i]){
.... your stuff, preferably replacing '&&' with '&' ....
} else {....}
}
Peter Ehlers
Thanks for any help
Wade
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
