[R] tapply on multiple groups

[David Winsemius]

On Jan 28, 2010, at 10:26 AM, GL wrote:

>
> Can you make tapply break down groups similar to bwplot or such?  
> Example:
>
> Data frame has one measure (Days) and two Dimensions (YYYYMM and  
> Place). All
> have the same length.
>
>> length(dbs.final$Days)
> [1] 3306
>> length()
> [1] 3306
>> length()
> [1] 3306
>
> Doing the following makes a nice table for one dimension and one  
> measure:
>
>    do.call(rbind,tapply(dbs.final$Days,dbs.final$Place, summary))
>
> But, what I really need to do is break it down on two dimensions and  
> one
> measures - effectively equivalent to the following bwplot call:
>
>    bwplot( Days ~ YYYYMM | Place, ,data=dbs.final)
>
> Is there an equivalent to the "|" operation in tapply?

Please reread the help page for tapply.

Perhaps?:

tapply(dbs.final$Days, list(dbs.final$YYYYMM, dbs.final$Place) summary)

-- David

>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT