R help - Mar 2006 - filtering in aggregate

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

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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