[R] dataframe question

[David Winsemius]

On Feb 7, 2010, at 8:14 PM, David Winsemius wrote:

>
> On Feb 7, 2010, at 7:51 PM, Vadlamani, Satish {FLNA} wrote:
>
>> Folks:
>> Good day. Please see the code below. three_wk_out is a dataframe  
>> with columns wk1 through wk209. I want to change the format of the  
>> columns. I am trying the code below but it does not work.  I need  
>> $week in the for loop interpreted as wk1, wk2, etc. Could you  
>> please help? Thanks.
>> Satish
>>
>> R code below
>> week_list <- paste("wk",c(1:209),sep="")
>
>
> Or more "functionally":
>
> three_wk_out <- as.data.frame( lapply(three_wk_out, some_function) )

Or if you wanted to just change the particular columns that matched  
the "wk" pattern:

idx <- grep("wk", names(three_wk_out))
three_wk_out[, idx ] <- apply( three_wk_out[, idx ], 2, as.numeric)


(I probably should have used apply( ___ , 2,  fn) in the prior effort  
rather than coercing a list back to a dataframe.)


>
> E.g.:
> >

>  a b c x
> 1 1 0 0 1
> 2 2 3 2 4
> 3 1 2 1 5
> 4 2 0 3 2
>
> > df <- as.data.frame(lapply(df, "^", 2))
> > df
>   a  b  c   x
> 1  1  0  0   1
> 2 16 81 16 256
> 3  1 16  1 625
> 4 16  0 81  16
>
>
>> for (week in week_list)
>> {
>>       three_wk_out$week <- as.numeric(three_wk_out$week)
>> }
>>
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>> 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.