[R] Summary of data.frame according to colnames and grouping factor

[David Winsemius]

If you prefer to do it with base functions, you could start by  
thinking about one column at a time, for which the tapply function is  
a logical choice:

 > tapply(d[,"A"], e, sum)
r s
3 6

Then wrap that in an apply call that handles each column sequentially:
 > apply(d, 2, function (x) tapply(x, e, sum)  )
   A B C
r 3 4 3
s 6 3 4

If you wanted a count of other logical "events", say the number of  
zeros, you could "sum" a logical function as s:
 > apply(d, 2, function (x) tapply(x, e, function (y) sum(y == 0)))
   A B C
r 7 6 7
s 4 7 6


--

On Mar 8, 2009, at 1:23 PM, baptiste auguie wrote:

> Hi,
>
> You could use the reshape package:
>
>
>> d$e <- e
>>
>> recast(d, variable~e, fun=sum)
>
>
> The doBy package is another option.
>
> baptiste
>
> On 8 Mar 2009, at 17:14, soeren.vogel at eawag.ch wrote:
>
>> A dataframe holds 3 vars, each checked true or false (1, 0). Another
>> var holds the grouping, r and s:
>>
>> ### start:example
>> set.seed(20)
>> d <- data.frame(sample(c(0, 1), 20, replace=T), sample(c(0, 1), 20,
>> replace=T), sample(c(0, 1), 20, replace=T))
>> names(d) <- c("A", "B", "C")
>> e <- rep(c("r", "s"), 10)
>> ### end:example
>>
>> How do I get the count of "1's" (or any other function) applied over
>> each var according to the grouping? That is:
>>
>> Desired output table:
>>
>>       A      B      C
>> r  count  count  count
>> s    ...    ...    ...
>>
>> or likewise transposed. I'd like to use the table for textual display
>> and/or barplot creation.
>>
>> Thx, Sören
>>
>> --
>> Sören Vogel, PhD-Student, Eawag, Dept. SIAM
>> http://www.eawag.ch, http://sozmod.eawag.ch
>>
>> ______________________________________________
>> 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.
>
> _____________________________
>
> Baptiste Auguié
>
> School of Physics
> University of Exeter
> Stocker Road,
> Exeter, Devon,
> EX4 4QL, UK
>
> Phone: +44 1392 264187
>
> http://newton.ex.ac.uk/research/emag
>
> ______________________________________________
> 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.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT