[R] filtering in aggregate

[Gabor Grothendieck]

Here is an example using the builtin data set, CO2, where we
aggregate uptake over Treatment for Plant equal to "Qn1" and
Type equal to "Quebec".

with(subset(CO2, subset = Plant == "Qn1" & Type == "Quebec"),
  aggregate(list(uptake = uptake), list(Treatment = Treatment), sum))

or equivalently:

with(CO2[CO2$Plant == "Qn1" & CO2$Type == "Quebec",],
  aggregate(list(uptake = uptake), list(Treatment = Treatment), sum))

or

CO2a <- CO2[CO2$Plant == "Qn1" & CO2$Type == "Quebec",]
aggregate(CO2a[,"uptake", drop=FALSE], CO2a[,"Treatment", drop=FALSE], sum)



On 3/14/06, Antonio Olinto <aolinto_r at bignet.com.br> wrote:
> Hello all,
>
> I have a data frame with year, month, species, fishing gear and catch
> (Y, M, S, F, C) and I want the sum of C by Y for species "A" and fishing
> gear "trawl".
>
> I tried things like aggregate(C[S=="A" & F=="trawl"], list (Year =
> Y[S=="A" & F=="trawl"]), fun=sum), but it didn't worked.
>
> To overcome this problem I did a subset as a new data frame and then I
> used aggregate. But I'm sure there's a way to apply a filter in data frame.
>
> Thanks for any help. Best regards.
>
> Antonio Olinto
>
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