[R] replace zeros for NA in a column based on values of another column

[arun]

HI,

Not sure I understand it correctly,

data1<-read.table(text="
 a      b      c      d
 0      1      1      0
 1      1      1      1
 1      0      0      1
",sep="",header=TRUE)
data2<- data1
data3<- data1
If i follow this logic for the 1st and 2nd columns,
 data1[ data1[ , 4 ] == 0 , 1 ] <- NA
 data1[ data1[ , 4 ] == 0 , 2 ] <- NA
 data1
#   a  b c d
#1 NA NA 1 0
#2  1  1 1 1
#3  1  0 0 1

Still, the column 'b' with 0 element is left as such while and `1` in b is replaced with NA

  data2[,1][data2[,4]==0 & data2[,1]==0]<- NA
 data2[,2][data2[,4]==0 & data2[,2]==0]<- NA
 data2
#   a b c d
#1 NA 1 1 0
#2  1 1 1 1
#3  1 0 0 1

#or you can try
data3[,1:2]<- lapply(letters[1:2],function(x) {x1<-cbind(data3[,x],data3[,4]);colnames(x1)<- c(x,"d");x1; x1[rowSums(x1)==0,1]<-NA;x1[,1]})
 data3
#   a b c d
#1 NA 1 1 0
#2  1 1 1 1
#3  1 0 0 1

A.K.




----- Original Message -----
From: Anthony Damico <ajdamico at gmail.com>
To: Camilo Mora <cmora at dal.ca>
Cc: R help <r-help at r-project.org>
Sent: Saturday, March 2, 2013 6:10 AM
Subject: Re: [R] replace zeros for NA in a column based on values of another column

you want to replace all rows where the 4th column is zero..  (data[ , 4 ]
== 0)
and you want to perform that replacement in the first column..

so try

data[ data[ , 4 ] == 0 , 1 ] <- NA



On Sat, Mar 2, 2013 at 5:26 AM, Camilo Mora <cmora at dal.ca> wrote:

> Hi everyone,
>
> Imagine that I have a data frame with four columns:
> data<-
> a       b       c       d
> 0       1       1       0
> 1       1       1       1
> 1       0       0       1
>
> I want to replace the zeros in columns a:b for NA only for the rows in
> which column d are zero. So
>
> a       b       c       d
> NA      1       1       0
> 1       1       1       1
> 1       0       0       1
>
> I am trying this:
> data[,1:3][data[4] == 0] <- NA
> But get this error:
>
> Error in `[<-.data.frame`(`*tmp*`, Data[4] == 0, value = NA) :
>   only logical matrix subscripts are allowed in replacement
>
> Does anyone knows the reason of this error or is there an alternative to
> replace the values in one column based on the values of another?
>
> Thanks,
>
> Camilo
>
> Camilo Mora, Ph.D.
> Department of Geography, University of Hawaii
> http://www.soc.hawaii.edu/**mora/ <http://www.soc.hawaii.edu/mora/>
>
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