Dear R-ers,
My aggregation saga continues.
Using the following sequence, I can calculate any statistic for row
groups and merge the result back to all associated rows ...
> WM = by( D60, D60[ "KeyProfA"], FUN=function(x) weighted.mean( x$IAC, x$Wt))
> D60$IAC.WM = as.numeric( WM[ D60$KeyProfA])
> class( WM)
[1] "by"
Questions ...
1) Is this a reasonable way to obtain the desired result?
2) What can one glean by knowing the class of WM ("by")? It appears
to me that class is a pretty shallow attribute in R ... just an
associated string that selects among methods in some contexts. Is
that really all there is to it? Is there a way to discover what
generic methods are aware of a given class? In other words, who
cares if WM is a "by" ... what does that do for me?
In my traditional universe (C++) I can grep and discover what methods
are virtual, who inherits from whom, etc. In R, the documentation
appears silent on what is a "by" (correct me if I'm wrong). In
addition, I have found no way to broadly search code to learn
things. (Displaying single functions is useful but hardly broad.)
How does one learn R more efficiently than randomly discovering how
to avoid error messages? (For example, I now know that a "by" cannot
be coerced into a data.frame (although it seems to me that such a
conversion could be usefully defined), so now I don't hit myself on
the head with that particular hammer.)
Chip Barnaby
---------------------------------------------------------
Chip Barnaby [EMAIL PROTECTED]
Vice President of Research
Wrightsoft Corp. 781-862-8719 x118 voice
131 Hartwell Ave 781-861-2058 fax
Lexington, MA 02421 www.wrightsoft.com
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