R help - Jul 2008 - set values in data.frame to NA conditional on another data.frame

Hello List,

Is there a faster way to set values in one data.frame equal to NA 
conditional on the corresponding value in another data.frame? Currently 
I am using:
 > b[is.na(a)] <- NA
where 'a' and 'b' are data.frames of equal size/dimensions, and
'a'
contains NAs but 'b' does not. This is extremely slow as is, as my 
data.frames are about 6000 columns by 6000 rows in size.
Are there any tricks to speed things up here?

Thank you in advance,

Carson

Hi

is your data all numeric or all character? If yes you can transform it to 
matrix and then such setting shall be quite quick.

vec<-rnorm(6000*6000)
mat<-vec
dim(mat)<-c(6000,6000)
mat2<-mat
mat2[sample(1:6000, 500), sample(1:6000, 500)]<-NA
sum(is.na(mat2))
[1] 250000
> 500*500
[1] 250000
system.time(mat[is.na(mat2)]<-NA)
   user  system elapsed 
   0.61    0.11    0.72 
>
> sum(is.na(mat))
[1] 250000

Regards
Petr

r-help-bounces at r-project.org napsal dne 02.07.2008 23:17:44:
> Hello List,
> 
> Is there a faster way to set values in one data.frame equal to NA 
> conditional on the corresponding value in another data.frame? Currently 
> I am using:
>  > b[is.na(a)] <- NA
> where 'a' and 'b' are data.frames of equal size/dimensions,
and 'a'
> contains NAs but 'b' does not. This is extremely slow as is, as my 
> data.frames are about 6000 columns by 6000 rows in size.
> Are there any tricks to speed things up here?
> 
> Thank you in advance,
> 
> Carson
> 
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