Hello R Helpers, After spending considerable time attempting to write a loop (and searching the help archives) I have decided to post my problem. In a dataframe I have columns labeled: q33a q33b q33c...q33r q35a q35b q35c...q35r What I want to do is create new variables based on the following logic: newfielda <- ifelse(q35a==1, q33a, NA) newfieldb <- ifelse(q35b==1, q33b, NA) ... newfieldr What I did was create two new dataframes, one containing q33a-r the other q35a-r and tried to loop over both, but I could not get any of the loop syntax I tried to give me the result I was seeking. Any help would be much appreciated. Greg Blevins Partner The Market Solutions Group, Inc. Minneapolis, MN Windows XP, R 2.1.1
Seeking help with a loop
3 messages · Greg Blevins, Tony Plate, Jean Eid
x <- data.frame(q33a=3:4,q33b=5:6,q35a=1:2,q35b=2:1)
> y <- list()
> for (i in grep("q33", colnames(x), value=TRUE))
+ y[[sub("q33","",i)]] <- ifelse(x[[sub("q33","q35",i)]]==1, x[[i]], NA)
> as.data.frame(y)
a b
1 3 NA
2 NA 6
> # if you really want to create new variables rather
> # than have them in a data frame:
> # (use paste() or sub() to modify the names if you
> # want something like "newfielda")
> for (i in names(y)) assign(i, y[[i]])
> a
[1] 3 NA
> b
[1] NA 6
>
hope this helps,
Tony Plate
Greg Blevins wrote:
Hello R Helpers, After spending considerable time attempting to write a loop (and searching the help archives) I have decided to post my problem. In a dataframe I have columns labeled: q33a q33b q33c...q33r q35a q35b q35c...q35r What I want to do is create new variables based on the following logic: newfielda <- ifelse(q35a==1, q33a, NA) newfieldb <- ifelse(q35b==1, q33b, NA) ... newfieldr What I did was create two new dataframes, one containing q33a-r the other q35a-r and tried to loop over both, but I could not get any of the loop syntax I tried to give me the result I was seeking. Any help would be much appreciated. Greg Blevins Partner The Market Solutions Group, Inc. Minneapolis, MN Windows XP, R 2.1.1
______________________________________________ R-help at stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
You can do the following without resorting to a "hard coded" loop
sapply( paste("q35", letters[1:grep("r", letters)], sep=""), function(x)
ifelse(temp[, x]%in%1,temp[, sub("5", "3", x)],NA)
as the following example shows
temp <- matrix(sample(c(0,1), 360, replace=T), nrow=10)
colnames(temp) <- c(paste("q33", letters[1:grep("r", letters)], sep=""), paste("q35", letters[1:grep("r", letters)], sep=""))
sapply( paste("q35", letters[1:grep("r", letters)], sep=""), function(x) ifelse(temp[, x]%in%1,temp[, sub("5", "3", x)],NA))
HTH
Jean
On Wed, 3 Aug 2005, Greg Blevins wrote:
Hello R Helpers, After spending considerable time attempting to write a loop (and searching the help archives) I have decided to post my problem. In a dataframe I have columns labeled: q33a q33b q33c...q33r q35a q35b q35c...q35r What I want to do is create new variables based on the following logic: newfielda <- ifelse(q35a==1, q33a, NA) newfieldb <- ifelse(q35b==1, q33b, NA) ... newfieldr What I did was create two new dataframes, one containing q33a-r the other q35a-r and tried to loop over both, but I could not get any of the loop syntax I tried to give me the result I was seeking. Any help would be much appreciated. Greg Blevins Partner The Market Solutions Group, Inc. Minneapolis, MN Windows XP, R 2.1.1
______________________________________________ R-help at stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html