[R] replace multiple values in vector at once

[Bert Gunter]

David is right, but it's trivial if x is a factor (which is the
default when you create character columns in a data frame).

(Note also how to use rep() properly -- read the docs: ?rep)

x <- factor(rep(LETTERS[1:3],e=3))
x
[1] A A A B B B C C C
Levels: A B C

levels(x) <- 1:3
x
[1] 1 1 1 2 2 2 3 3 3
Levels: 1 2 3

Cheers,
Bert
On Fri, Jul 12, 2013 at 3:05 PM, David Winsemius <dwinsemius at comcast.net> wrote:
>
> On Jul 12, 2013, at 2:56 PM, Trevor Davies wrote:
>
>> I always think that replying to your own r-help feels silly but it's good
>> to close these things out.
>>
>> here's my hack solution:
>>
>> x1<-merge(data.frame(A=x),data.frame(A=c('x','y','z'),B=c(1,2,2)),by='A')[,2]
>
> That fairly tortured compared with:
>
> x <- c(rep('x',3),rep('y',3),rep('z',3))
>
> x1b <- as.character(1:3)[ match(x, c("x","y","z") ) ]
> x1b
>
> Furthermore, your solution does not deliver the answer you expected.
>
> --
> David.
>
>>
>> Well that works and should for my more complex situation.  If anyone has
>> something a little less heavy handed I'd live to hear it.
>>
>> Have a great weekend.
>>
>>
>> On Fri, Jul 12, 2013 at 2:18 PM, Trevor Davies <davies.trevor at gmail.com>wrote:
>>
>>>
>>> I'm trying to find a function that can replace multiple instances of
>>> values or characters in a vector in a one step operation.  As an example,
>>> the vector:
>>>
>>> x <- c(rep('x',3),rep('y',3),rep('z',3))
>>>
>>>> x
>>> [1] "x" "x" "x" "y" "y" "y" "z" "z" "z"
>>>
>>> I would simply like to replace all of the x's with 1's, y:2 & z:3 (or
>>> other characters).
>>> i.e:
>>>> x
>>> [1] "1" "1" "1" "2" "2" "2" "3" "3" "3"
>>>
>>> Of course, I'm aware of the replace function but this obviously gets a
>>> little unwieldy when there are :
>>> x<-replace(x,x=='x',1)
>>> x<-replace(x,y=='x',2)
>>> x<-replace(x,z=='x',3)
>>>
>>> but I can't figure out how to do it in a one stop operation.  My real
>>> needs is more complex obviously.  This is one of those seemingly simple
>>> r-operations that should be obvious but I'm coming up empty on this one.
>>>
>>> Thanks for the help.
>>> Trevor
>>>
>>
>>       [[alternative HTML version deleted]]
>>
>> ______________________________________________
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>> 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.
>
> David Winsemius
> Alameda, CA, USA
>
> ______________________________________________
> 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.



-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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