R help - Jan 2010 - Replacing NAs with 0 for variables with the same ending

Dear all,

I'm looking for a way to replace NA's with 0 for a number of variables
which share the same ending and which constitute a subset of a data frame.

Say, for example, there is
> data <- data.frame(ax=c(1,2,3,NA,0) , bx=c(3,5,NA,5,1) ,
ay=c(5,NA,2,NA,0) , by=c(4,2,NA,2,1))
> data
  ax bx ay by
1  1  3  5  4
2  2  5 NA  2
3  3 NA  2 NA
4 NA  5 NA  2
5  0  1  0  1

I wish to apply something like  //
//
/> data[is.na(data)] <- 0/
//
but not to the entire data frame, rather only to the variables ending
with x.

There should be something which emulates the use of a wildcard, ie.
which makes the operation being carried out for all variables "*x". I
tried with grep and glob2rx but did not succeed.

Many thanks for any hints!

Uli Kleinwechter


-- 
Uli Kleinwechter
Agricultural and Food Policy Group (420a)
Faculty of Agricultural Sciences
University of Hohenheim
D-70593 Stuttgart
Phone: (+49) 711 459-22656
Fax: (+49) 711 459-23752
E-mail: u.kleinwechter at uni-hohenheim.de
http://www.uni-hohenheim.de/apo

On 01/15/2010 07:10 PM, Uli Kleinwechter wrote:
> Dear all,
>
> I'm looking for a way to replace NA's with 0 for a number of
variables
> which share the same ending and which constitute a subset of a data frame.
>
> Say, for example, there is
>
>> data<- data.frame(ax=c(1,2,3,NA,0) , bx=c(3,5,NA,5,1) ,
> ay=c(5,NA,2,NA,0) , by=c(4,2,NA,2,1))
>> data
>    ax bx ay by
> 1  1  3  5  4
> 2  2  5 NA  2
> 3  3 NA  2 NA
> 4 NA  5 NA  2
> 5  0  1  0  1
>
> I wish to apply something like  //
> //
> />  data[is.na(data)]<- 0/
> //
> but not to the entire data frame, rather only to the variables ending
> with x.
>
Hi Uli,
How about:

data[,grep("x",names(data))][is.na(data[,grep("x",names(data))])]<-0

Jim