R help - Sep 2010 - subbing a string vector for another string vector

I have a data frame with two columns:
      image                               pattern
1    http://$IMAGE_ID$            www.url.com/image.jpg
2    $IMAGE_ID$                      http://www.blah.com/image.gif
...

I want to replace "$IMAGE_ID$" with the corresponding entry in the
pattern
column such that the result would appear as follows:

url
http://www.url.com/image.jpg
http://www.blah.com/image.gif

Using something like  > gsub("\\$IMAGE\\_ID\\$",image,pattern)
doesn't work
because it only takes uses the first entry in "pattern" as the
replacement
for all "image" entries:

url
http://www.url.com/image.jpg
www.url.com/image.jpg

Please help.
Thanks.




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On Sep 8, 2010, at 4:45 PM, jlemaitre wrote:
>
> I have a data frame with two columns:
>       url.img                               patt.url
> 1    http://$IMAGE_ID$            www.url.com/image.jpg
> 2    $IMAGE_ID$                      http://www.blah.com/image.gif
> ...
>
> I want to replace "$IMAGE_ID$" with the corresponding entry in
the
> pattern
> column such that the result would appear as follows:
A) Drop the use of the name "pattern" because it is the argument name
for regex functions. Name it something else like "patt.url".  
Furthermore "image" is also a function name so use somehting more  
specific there too, say "url.img"

B) use grep(<grep-pattern>, df$url.img) to identify the rows of  
"patt.url" you want to assemble.

Perhaps:

df[ grep("\\$IMAGE\\_ID\\$", df$url.img), "patt.url"]

>
> url
> http://www.url.com/image.jpg
> http://www.blah.com/image.gif
>
> Using something like  > gsub(,image,pattern) doesn't work
> because it only takes uses the first entry in "pattern" as the  
> replacement
> for all "image" entries:
>
> url
> http://www.url.com/image.jpg
> www.url.com/image.jpg
>
> Please help.
> Thanks.
>
>
>
>
> -- 
> View this message in context:
http://r.789695.n4.nabble.com/subbing-a-string-vector-for-another-string-vector-tp2532005p2532005.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at 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.
David Winsemius, MD
West Hartford, CT

One way to do it is with mapply:
> mydf =
data.frame(image=c('http://$IMAGE_ID$','$IMAGE_ID$'),pattern=c('www.url.com/image.jpg','http://www.blah.com/image.gif'))
> mydf$url  = mapply(sub,"\\$IMAGE_ID\\$",mydf$pattern,mydf$image)
> mydf
               image                       pattern                           url
1 http://$IMAGE_ID$         www.url.com/image.jpg  http://www.url.com/image.jpg
2        $IMAGE_ID$ http://www.blah.com/image.gif http://www.blah.com/image.gif

 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu




On Wed, 8 Sep 2010, jlemaitre wrote:
>
> I have a data frame with two columns:
>      image                               pattern
> 1    http://$IMAGE_ID$            www.url.com/image.jpg
> 2    $IMAGE_ID$                      http://www.blah.com/image.gif
> ...
>
> I want to replace "$IMAGE_ID$" with the corresponding entry in
the pattern
> column such that the result would appear as follows:
>
> url
> http://www.url.com/image.jpg
> http://www.blah.com/image.gif
>
> Using something like  > gsub("\\$IMAGE\\_ID\\$",image,pattern)
doesn't work
> because it only takes uses the first entry in "pattern" as the
replacement
> for all "image" entries:
>
> url
> http://www.url.com/image.jpg
> www.url.com/image.jpg
>
> Please help.
> Thanks.
>
>
>
>
> -- 
> View this message in context:
http://r.789695.n4.nabble.com/subbing-a-string-vector-for-another-string-vector-tp2532005p2532005.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at 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.
>