On Dec 8, 2010, at 3:10 PM, 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.
That looks really, really painful. Why not use the function
findInterval and then do a lookup in a character vector. Then you can
throw away that loopy construct completely.
> demo <- data.frame(Area = runif(10, 0, 100))
> demo$catarea <- findInterval(demo$Area, c(0,25,50,75,100))
> demo
Area catarea
1 71.440401 3
2 8.438097 1
3 45.492178 2
4 50.669996 3
5 15.444114 1
6 33.954948 2
7 19.738747 1
8 56.485654 3
9 29.218921 2
10 74.204611 3
> demo$catname <- c("S01","S02", "S03","S04")[demo$catarea]
> demo
Area catarea catname
1 71.440401 3 S03
2 8.438097 1 S01
3 45.492178 2 S02
4 50.669996 3 S03
5 15.444114 1 S01
6 33.954948 2 S02
7 19.738747 1 S01
8 56.485654 3 S03
9 29.218921 2 S02
10 74.204611 3 S03
--
David.
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"
Thanks for any help
Wade
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David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
