R help - Oct 2011 - function - access column

How can I call matrix$col, inside a function?
The matrix name is one of the variables of the function, while the
column name I get by assuming that it should have a certain
characters.

something like this

function(matrix){
colname=as.name(grep("[A-T a-t]ting",colnames(matrix),value=TRUE))
output=2*(matrix$colname)
return(output)
}

The name of the column is Testing.

Perhaps something like this:

Test <- function(m){
     m <- if(is.character(m)) get(m) else m
     stopifnot(length(colnames(m))>0)
     n = colnames(m)
     # Process n however
     2* m[, n]
}

That make sense?

Hope it helps,
Michael


On Oct 7, 2011, at 11:03 AM, Ana <rrasterr at gmail.com> wrote:
> How can I call matrix$col, inside a function?
> The matrix name is one of the variables of the function, while the
> column name I get by assuming that it should have a certain
> characters.
> 
> something like this
> 
> function(matrix){
> colname=as.name(grep("[A-T
a-t]ting",colnames(matrix),value=TRUE))
> output=2*(matrix$colname)
> return(output)
> }
> 
> The name of the column is Testing.
> 
> ______________________________________________
> 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.

Thanks! It helps. I completely forgot about the colnames function

I added a "which(colnames(m)==n)" to my own function and now I can
access with no problem the column by the number instead of the name.




On Fri, Oct 7, 2011 at 5:09 PM, R. Michael Weylandt
<michael.weylandt at gmail.com> <michael.weylandt at gmail.com>
wrote:
> Perhaps something like this:
>
> Test <- function(m){
> ? ? m <- if(is.character(m)) get(m) else m
> ? ? stopifnot(length(colnames(m))>0)
> ? ? n = colnames(m)
> ? ? # Process n however
> ? ? 2* m[, n]
> }
>
> That make sense?
>
> Hope it helps,
> Michael
>
>
> On Oct 7, 2011, at 11:03 AM, Ana <rrasterr at gmail.com> wrote:
>
>> How can I call matrix$col, inside a function?
>> The matrix name is one of the variables of the function, while the
>> column name I get by assuming that it should have a certain
>> characters.
>>
>> something like this
>>
>> function(matrix){
>> colname=as.name(grep("[A-T
a-t]ting",colnames(matrix),value=TRUE))
>> output=2*(matrix$colname)
>> return(output)
>> }
>>
>> The name of the column is Testing.
>>
>> ______________________________________________
>> 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.
>