On Sep 1, 2010, at 6:29 PM, Adrian Ng wrote:
Dear R-Users,
I have been using R for about 1 week and recently learned about the
Aggregate function, and from reading online it seems like it is
comparable to a SQL group by to perform summary functions. I am
looking to do a summary function, such as SUM/MIN, but instead of
these basic functions, I would like to calculate the IRR.
Assuming I have a data set DS01:
FirstName LastName NCF Date
A B -100
1/1/2001
A B 50
2/1/2002
A B 200
3/1/2003
A C -500
1/1/2001
A C 50
2/1/2002
A C 70
3/1/2003
A C 50
2/1/2004
A C 70
3/1/2005
And an IRR function which takes in a cash flow and dates as inputs:
IRR(NCF,cfDate) and returns the IRR
I tried the following:
aggregate(DS01$NCF,by=list(DS01$ FirstName,DS01$
LastName),RR,cfDate=DS01$Date)
Since you are not forthcoming with the code for IRR (nor did you even
spell it correctly in your aggregate call), I will simple suggest that
you consider using the functions from the plyr package or if you
wanted to do it the old way you could look up split() and do :
lapply (split(DS01, list(DS01$ FirstName,DS01$ LastName), IRR(NCF,
cfDate=Date) ).
Plyr method (perhaps):
require(plyr)
ddply(DS01, .( FirstName, LastName), function(df) IRR(NCF,
cfDate=Date) )
I'm quite sure that the data.table functionality could handle it quite
easily as well.
and I got the following error:
Error in aggregate.data.frame(as.data.frame(x), ...) :
arguments must have same length
If anyone could shed some light on what may be causing this that
would be great.
aggregate() takes a vector while you need to pass a more complex
structure. I think you passed the entire length of Date.
More importantly, is this the right way to do this (should I even be
using the aggregate function)?
Any help would be greatly appreciated!
Thanks!
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