[R] FUN argument to return a vector in aggregate function

[utkarshsinghal]

Extending my question further, I want to apply different FUN arguments 
on three fields and the "by" argument also contains more than one field.
For example:
set.seed(100)
d = 
data.frame(a=sample(letters[1:2],20,replace=T),b=sample(3,20,replace=T),c=rpois(20,1),d=rbinom(20,1,0.5),e=rep(c("X","Y"),10))

Now I want to split by fields "a" and "b", and want to calculate 
mean(c), sum(d) and "X"%in%e.

Is there any function which can do this and return the output in a 
dataframe format. For the above example, it should ideally be a 6*5 
dataframe.

Thanks in advance.

Regards,
Utkarsh Singhal



On 11/23/2009 5:14 AM, Gabor Grothendieck wrote:
> Try this:
>
>    
>> library(doBy)
>> summaryBy(breaks ~ ., warpbreaks, FUN = c(mean, sum, length))
>>      
>    wool tension breaks.mean breaks.sum breaks.length
> 1    A       L    44.55556        401             9
> 2    A       M    24.00000        216             9
> 3    A       H    24.55556        221             9
> 4    B       L    28.22222        254             9
> 5    B       M    28.77778        259             9
> 6    B       H    18.77778        169             9
>
> On Mon, Nov 23, 2009 at 3:15 AM, utkarshsinghal
> <utkarsh.singhal at global-analytics.com>  wrote:
>    
>> Hi All,
>>
>> I am currently doing the following to compute summary statistics of
>> aggregated data:
>> a = aggregate(warpbreaks$breaks, warpbreaks[,-1], mean)
>> b = aggregate(warpbreaks$breaks, warpbreaks[,-1], sum)
>> c = aggregate(warpbreaks$breaks, warpbreaks[,-1], length)
>> ans = cbind(a, b[,3], c[,3])
>>
>> This seems unnecessarily complex to me so I tried
>>      
>>> aggregate(warpbreaks$breaks, warpbreaks[,-1], function(z)
>>> c(mean(z),sum(z),length(z)))
>>>        
>> but aggregate doesn't allow FUN argument to return a vector.
>>
>> I tried "by", "tapply" and several other functions as well but the output
>> needed further modifications to get the same format as "ans" above.
>>
>> Is there any other function same as aggregate which allow FUN argument to
>> return vector.
>>
>> Regards
>> Utkarsh
>>
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>>      
>
>