Message-ID: <42F38805.3090303@pdf.com>
Date: 2005-08-05T15:38:45Z
From: Sundar Dorai-Raj
Subject: use of NA's
In-Reply-To: <1123241457.3951.6.camel@localhost.localdomain>
tom wright wrote:
> Can someone please explain why this works:
>
>
>>>d<-c(0,2,3,2,0,3,4,0,0,0,0,0)
>>>d.mat<-matrix(data=d,nrow=4,ncol=3,byrow=TRUE)
>>>for(i in 1:length(d.mat[1,])){
>>
>>+ d.mat[,i][d.mat[,i]==0]<-mean(d.mat[,i][d.mat[,i]>0])
>>+ }
>
>
> Whereas:
>
>
>>d<-c(0,2,3,2,0,3,4,0,0,0,0,0)
>>d.mat<-matrix(data=d,nrow=4,ncol=3,byrow=TRUE)
>>d.mat[d.mat==0]<-NA
>>for(i in 1:length(d.mat[1,])){
>
> + d.mat[,i][d.mat[,i]==NA]<-mean(d.mat[,i],na.rm=TRUE)
> + }
> dosnt
>
> Thanks
> Tom
>
d.mat[,i] == NA returns NA. You want ?is.na to test for missing values.
--sundar