[R] operator problem within function

[David Winsemius]

On Apr 28, 2010, at 5:45 PM, David Winsemius wrote:

>
> On Apr 28, 2010, at 5:31 PM, Bunny, lautloscrew.com wrote:
>
>> Dear all,
>>
>> i have a problem with processing dataframes within a function using  
>> the "$".
>> Here´s my code:
>>
>>
>> recode_items = function(dataframe,number,medium=2){
>> 	
>> 	# this works
>> 	q<-paste("columna",number,sep="")
>
> Do your really want q to equal "columna2" when "number" equals 2?
>
>>
>> 	# this does not work, particularly because "dataframe" is not  
>> processed
>> 	# dataframe should be: givenframe$columnagivennumber
>> 	a=dataframe$q[dataframe$q==medium]=1

Did you want a further logical test with that "=1" or some sort of  
assignment???

>
> a) Do you want to work on the column from dataframe ( horrible name  
> for this purpose IMO) with the name "columna2"? If so, then start with
>
> dataframe[ , q ]
>
> .... the "q" will be evaluated in this form whereas it would not  
> when used with "$".
>
> b) (A guess in absence of explanation of a goal.) Now do you want  
> all of the rows where that vector equals "medium"? If so ,then try  
> this:
>
> dataframe[ dataframe[ , q ]==2 , ]  # untested in the absence of data

Ooops. should have been:

dataframe[ dataframe[ , q ]==medium , ] #since both q and medium will  
be evaluated.


>
> Moral: Generally better to use "[" indexing.
>
> -- 
> David.
>
>
>>
>>
>> 	return(a)	
>>
>> }
>>
>>
>> If I call this function, i´d like it to return my  dataframe.  The  
>> problem appears to be somewhere around the $. I´m sure this not too  
>> hard, but somehow i am stuck. I´ll keep searchin the manuals.
>> Thx for any help in advance.
>>
>> best
>>
>> matt
>> 	[[alternative HTML version deleted]]
>>
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>
> ______________________________________________
> 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.