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
> 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
>