[R] R 3.1.2 using a custom function in aggregate() function on Windows 7 OS 64bit

[David Winsemius]

On Mar 4, 2015, at 2:02 PM, Typhenn Brichieri-Colombi via R-help wrote:

> Hello,
> 
> I am trying to use the following custom function in an aggregatefunction, but cannot get R to recognize my data. I’ve read the help on function()and on aggregate() but am unable to solve my problem. How can I get R torecognize the data inputs for the custom function nested within aggregate()?
> 
> My custom function is found below, as well as the errormessage I get when I run it on a test data set (I will be using this functionon a much larger dataset (over 600,000 rows)) 
> 
> Thank you for your time and your help!
>  
> d_rule<-function(a,x){ 
> i<-which(a==max(a))
> out<-ifelse(length(i)==1, x[i], min(x))
> return(out)
> }
>  
> a<-c(2,2,1,4,2,5,2,3,4,4)
> x<-c(1:10)
> g<-c(1,1,2,2,3,3,4,4,5,5)
> dat<-as.data.frame(cbind(x,g))
>  
> test<-aggregate(dat, by=list(g), FUN=d_rule,dat$a, dat$x)
> 
> Error in dat$x : $ operator is invalid for atomic vectors

That message makes no sense to me because it suggests that the 'dat'-object was not a dataframe.

I get a different error which I think I can explain:

> test<-aggregate(dat, by=list(g), FUN=d_rule,dat$a, dat$x)
Error in FUN(X[[1L]], ...) : 
  unused argument (c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10))

The aggregate.data.frame function is I believe one by one positionally matching  the x and g columns to the a-parameter of the d_rule-function and would be attempting to use dat$a (which as far as I can tell doesn't exist and would throw an error if the interpreter ever got to that step)  as the match to the d_rule x-parameter, but before it does that, it tries to match dat$x to some parameter in d_rule but because both parameters already have candidate objects matched up, it fails producing the error message I see.

(It's also very bad practice to use the construction as.data.frame(cbind(x,g)). It will mangle the results if there are either factor or character variables inside the cbind().

-- 
David.
> 
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David Winsemius
Alameda, CA, USA