[R] identify an element in a column

[Ivan Calandra]

Another way is with ifelse:
z<-data.frame(x,y)
z$y2 <- ifelse(z$x==5,z$y-1,z$y)

HTH,
Ivan

Le 2/22/2011 18:27, Erik Iverson a écrit :
> Is this what you mean?
>
> z[which(z[,"x"] == 5) - 1, "y"]
>
> ?which is probably what you're looking for...
>
> Hongwei Dong wrote:
>> Hi, R users,
>>
>> I'm wondering if I can identify an element in a column by an element in
>> another column. For example:
>>
>> x<-1:10
>> y<-11:20
>> z<-cbind(x,y)
>> z
>>      x  y
>>  [1,]  1 11
>>  [2,]  2 12
>>  [3,]  3 13
>>  [4,]  4 14
>>  [5,]  5 15
>>  [6,]  6 16
>>  [7,]  7 17
>>  [8,]  8 18
>>  [9,]  9 19
>> [10,] 10 20
>>
>> What I want to do is: when x=5, y=y-1
>>
>> Anyone can tell me how to do this? Thanks.
>>
>>
>> Gary
>>
>>     [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide 
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
Abt. Säugetiere
Martin-Luther-King-Platz 3
D-20146 Hamburg, GERMANY
+49(0)40 42838 6231
ivan.calandra at uni-hamburg.de

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