On Sep 15, 2011, at 4:07 PM, Jon Zadra wrote:
> Hi,
>
> I'm having some problems with the aggregate() function in the {stats}
> package, and the documentation doesn't address them.
>
> 1) Why would the first line work, but the second not? According to the help
> file, it accepts a "data=" argument.
>
>> with(tsrc, aggregate(x=DistRatio, by=list(Condition), FUN=mean))
> Group.1 x
> 1 Congruent 1.741789
> 2 Mismatch 1.771425
>
>> aggregate(x=DistRatio, by=list(Condition), data=tsrc, FUN=mean)
> Error in aggregate(x = DistRatio, by = list(Condition), data = tsrc, FUN =
> mean) :
> object 'DistRatio' not found
>
>
> 2) The subset argument also does not appear to work (perhaps this is the same
> issue?):
>
>> with(tsrc, aggregate(x=DistRatio, by=list(Condition), subset=Drop!="Yes",
>> FUN=mean))
> Group.1 x
> 1 Congruent 1.741789
> 2 Mismatch 1.771425
>
>> with(tsrc[tsrc$Drop!="Yes",], aggregate(x=DistRatio, by=list(Condition),
>> FUN=mean))
> Group.1 x
> 1 Congruent 1.700215
> 2 Mismatch 1.859795
>
>
> So, am I doing something wrong or is this function just not working as
> advertised?
>
> Thanks,
>
> Jon
You are combining syntax from the data frame method for aggregate() with
arguments (data and subset) that are only available in the formula method. Be
sure to read the help page for the function and note at the top of the page,
the different syntax for each method. Of course, note the examples as well.
If you want to use the formula method with 'data' and 'subset' you would need
to use something like:
aggregate(DistRatio ~ Condition, data = tsrc, FUN = mean)
or:
aggregate(DistRatio ~ Condition, data = tsrc, subset = Drop != "Yes", FUN =
mean)
HTH,
Marc Schwartz
______________________________________________
R-help@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.
