R help - Feb 2012 - How to replace the values in a column

Dear All,
I've been searching relevant topics about replacing values, none seemed to
be applicable to me...

I have a file with many many varieties, and want to replace some of them
into different names. 
I tried various of ways, still don't know how to do that most efficiently..
Here is part of the example data:


Gen    Rep
A_1      1
A_1       2 
A_2     1
A_2     2
B_1       1
B_1       2
B_3       1
B_3       2
OP1_1   1
OP1_1   2
OP1_5   1
OP1_5   2

For example, I want to replace  A_1,  B_3,  OP1_1 into different name
"Wynda"

So that the expected file should become:

Gen          Rep
Wynda      1
Wynda        2
A_2           1 
A_2           2
B_1              1
B_1             2
Wynda        1
Wynda        2
Wynda        1
Wynda        2
OP1_5          1
OP1_5         2


I have created a link file, which contains two rows, translating which Gen
correlating to which Name. Not sure if this file helps or not, example as
below:

Column1(Gen)        Column2(Name)
A_1                               Wynda
A_2                                 A_2
B_1                                 B_1
B_3                             Wynda
OP1_1                       Wynda
OP1_5                        OP1_5


Though I can replace one by one in excel, since there are too many files and
too many reps, it'll be very time-consuming also easy to make mistakes.

Please give me any guidance or help in terms of finish this with R.

Thanks so much !

Sincerely
Hannah



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Hannah,
If Gen is a factor you can simply build the new factor "on top" of it:

dataframe$Gen<- factor( c('Wynda' , 'A_2' , 'B_1' ,
'Wynda' , 'Wynda'
, 'OP1_5')[Gen] )

Just make sure the replacement labels are in the same order as levels(Gen).

Cheers

On Tue, Feb 28, 2012 at 8:39 PM, hannahmaohuang
<hannahmaohuang at gmail.com> wrote:
> Dear All,
> I've been searching relevant topics about replacing values, none seemed
to
> be applicable to me...
>
> I have a file with many many varieties, and want to replace some of them
> into different names.
> I tried various of ways, still don't know how to do that most
efficiently..
> Here is part of the example data:
>
>
> Gen ? ?Rep
> A_1 ? ? ?1
> A_1 ? ? ? 2
> A_2 ? ? 1
> A_2 ? ? 2
> B_1 ? ? ? 1
> B_1 ? ? ? 2
> B_3 ? ? ? 1
> B_3 ? ? ? 2
> OP1_1 ? 1
> OP1_1 ? 2
> OP1_5 ? 1
> OP1_5 ? 2
>
> For example, I want to replace ?A_1, ?B_3, ?OP1_1 into different name
> "Wynda"
>
> So that the expected file should become:
>
> Gen ? ? ? ? ?Rep
> Wynda ? ? ?1
> Wynda ? ? ? ?2
> A_2 ? ? ? ? ? 1
> A_2 ? ? ? ? ? 2
> B_1 ? ? ? ? ? ? ?1
> B_1 ? ? ? ? ? ? 2
> Wynda ? ? ? ?1
> Wynda ? ? ? ?2
> Wynda ? ? ? ?1
> Wynda ? ? ? ?2
> OP1_5 ? ? ? ? ?1
> OP1_5 ? ? ? ? 2
>
>
> I have created a link file, which contains two rows, translating which Gen
> correlating to which Name. Not sure if this file helps or not, example as
> below:
>
> Column1(Gen) ? ? ? ?Column2(Name)
> A_1 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Wynda
> A_2 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? A_2
> B_1 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? B_1
> B_3 ? ? ? ? ? ? ? ? ? ? ? ? ? ? Wynda
> OP1_1 ? ? ? ? ? ? ? ? ? ? ? Wynda
> OP1_5 ? ? ? ? ? ? ? ? ? ? ? ?OP1_5
>
>
> Though I can replace one by one in excel, since there are too many files
and
> too many reps, it'll be very time-consuming also easy to make mistakes.
>
> Please give me any guidance or help in terms of finish this with R.
>
> Thanks so much !
>
> Sincerely
> Hannah
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/How-to-replace-the-values-in-a-column-tp4430448p4430448.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.

Hello,

Try the following.
(In Andrija's code I've changed 'df' to 'DF',
'df' is a R function name)

DF <- read.table( ... etc ...

tc <- textConnection("
Column1(Gen)        Column2(Name)
A_1                               Wynda
A_2                                 A_2
B_1                                 B_1
B_3                             Wynda
OP1_1                       Wynda
OP1_5                        OP1_5 
")
TransTable <- read.table(tc, header=TRUE, stringsAsFactors=FALSE)
close(tc)

nrTrans <- nrow(TransTable)

for(iTrans in 1:nrTrans){
	i <- DF$Gen == TransTable[iTrans, 1]
	DF$Gen[i] <- TransTable[iTrans, 2]
}
# See first 6 lines of result
head(DF)

That's it.

Hope this helps,

Rui Barradas



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