[R] fun.aggregate=mean in reshape

[Sundar Dorai-Raj]

[Ricardo Rodriguez] Your XEN ICT Team said the following on 2/12/2008 
12:23 AM:
> Hi all,
> 
> We are facing a problem while introducing ourselves to Reshape package 
> use. Melt seems to work fine, but cast fails when we use mean as 
> fun.aggregate. As you see here, length and sum work fine, but mean 
> throws this same error whatever dataset we use.
> 
>  > cast(aqm, month ~ variable, length)
>   month ozone solar.r wind temp
> 1     5    26      27   31   31
> 2     6     9      30   30   30
> 3     7    26      31   31   31
> 4     8    26      28   31   31
> 5     9    29      30   30   30
>  > cast(aqm, month ~ variable, sum)
>   month ozone solar.r  wind temp
> 1     5   614    4895 360.3 2032
> 2     6   265    5705 308.0 2373
> 3     7  1537    6711 277.2 2601
> 4     8  1559    4812 272.6 2603
> 5     9   912    5023 305.4 2307
>  > cast(aqm, month ~ variable, mean)
> Error in get(as.character(FUN), mode = "function", envir = envir) :
>   variable "fun" of mode "function" was not found
>  >
> 
> 
> Our environment:
> 
>  > version
>                _                          
> platform       i386-apple-darwin8.10.1    
> arch           i386                       
> os             darwin8.10.1               
> system         i386, darwin8.10.1         
> status                                    
> major          2                          
> minor          6.2                        
> year           2008                       
> month          02                         
> day            08                         
> svn rev        44383                      
> language       R                          
> version.string R version 2.6.2 (2008-02-08)
> 
> 
>  > installed.packages()
> 
> reshape    "reshape"    
> "/Library/Frameworks/R.framework/Resources/library" "0.8.0"   
> NA            NA
> 
> 
> Please, could you help use to work out this issue? Thanks!
> 

Do you have an object called 'mean' that's masking the base::mean 
function? I can replicate your error using the following:

 > library(reshape)
 > names(airquality) <- tolower(names(airquality))
 > aqm <- melt(airquality, id=c("month", "day"), na.rm=TRUE)
 > mean <- 1
 > cast(aqm, month ~ variable, mean)
Error in get(as.character(FUN), mode = "function", envir = envir) :
   variable "fun" of mode "function" was not found
 > cast(aqm, month ~ variable, base::mean)
   month    ozone  solar.r      wind     temp
1     5 23.61538 181.2963 11.622581 65.54839
2     6 29.44444 190.1667 10.266667 79.10000
3     7 59.11538 216.4839  8.941935 83.90323
4     8 59.96154 171.8571  8.793548 83.96774
5     9 31.44828 167.4333 10.180000 76.90000
 > find("mean")
[1] ".GlobalEnv"   "package:base"


HTH,

--sundar