[R] cbind in aggregate formula - based on an existing object (vector)

[Dimitri Liakhovitski]

Thank you, David, it does work.
Could you please explain why? What exactly does changing it to "as matrix" do?
Thank you!
Dimitri

On Thu, Jul 14, 2011 at 3:25 PM, David Winsemius <dwinsemius at comcast.net> wrote:
>
> On Jul 14, 2011, at 3:05 PM, Dimitri Liakhovitski wrote:
>
>> Hello!
>>
>> I am aggregating using a formula in aggregate - of the type:
>> aggregate(cbind(var1,var2,var3)~factor1+factor2,sum,data=mydata)
>>
>> However, I actually have an object (vector of my variables to be
>> aggregated):
>> myvars<-c("var1","var2","var3")
>>
>> I'd like my aggregate formula (its "cbind" part) to be able to use my
>> "myvars" object. Is it possible?
>> Thanks for your help!
>>
>
> Not sure I have gotten all the way there, but this does work:
>
> example.agg1<-aggregate(as.matrix(example[myvars])~group+mydate,sum,data=example)
>
>> example.agg1
>   group     mydate example[myvars]    NA
> 1 group1 2008-12-01               4   4.2
> 2 group2 2008-12-01               6   6.2
> 3 group1 2009-01-01              40  40.2
> 4 group2 2009-01-01              60  60.2
> 5 group1 2009-02-01             400 400.2
> 6 group2 2009-02-01             600 600.2
>
>> Dimitri
>>
>> Reproducible example:
>>
>> mydate = rep(seq(as.Date("2008-12-01"), length = 3, by = "month"),4)
>> value1=c(1,10,100,2,20,200,3,30,300,4,40,400)
>> value2=c(1.1,10.1,100.1,2.1,20.1,200.1,3.1,30.1,300.1,4.1,40.1,400.1)
>>
>> example<-data.frame(mydate=mydate,value1=value1,value2=value2)
>>
>> example$group<-c(rep("group1",3),rep("group2",3),rep("group1",3),rep("group2",3))
>> example$group<-as.factor(example$group)
>> (example);str(example)
>>
>>
>> example.agg1<-aggregate(cbind(value1,value2)~group+mydate,sum,data=example)
>> # this works
>> (example.agg1)
>>
>> ### Building my object (vector of 2 names - in reality, many more):
>> myvars<-c("value1","value2")
>> example.agg1<-aggregate(cbind(myvars)~group+mydate,sum,data=example)
>> ### does not work
>>
>>
>> --
>> Dimitri Liakhovitski
>> Ninah Consulting
>> www.ninah.com
>>
>> ______________________________________________
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>> 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
> West Hartford, CT
>
>



-- 
Dimitri Liakhovitski
Ninah Consulting
www.ninah.com