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

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

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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