R help - Sep 2008 - additional parameters in function called by tapply

Der R-Gurus,
first apologies if this is a FAQ, but I  due to lack of R-knowledge and
terminology I wasn't able to find it.
I have the following problem in aggregating results of a model calculation:
The results are yearly values of several parameters with several hierarchical
spatial factors taken from a database as a data frame with the following
structure

value | year | spatial1  | spatial2 | spatial3 | parameter
the values are given for spatial1 units, i.e. the com
spatial3 contains one or many spatial2 units, spatial2 contains one or many
spatial1 units.
The normal aggregation goes in a two step way:

a) summation of the parameter values of the same spatial differentiaton (e.g.
sums of spatial2 or spatial3)
b) calculation of the average of several years of the sums

for step a I use tapply with the following call

indices <- (list(year,spatial2,parameter)
resultspatial <- tapply(value,indices,sum)

for step b I use apply with the result of a and  a function block_average
block_average <- funcition(value,year,number_of_years_to_average) with the
parameters value and years as vectors and number_of_years as integer.

When I'm trying to skip the spatial aggregation, i.e. just do the
block_averaging over years, I have the problem (AFIU the man page), that I
can't provide the years vector as parameter to the function block_average
via tapply. What would be the R-ish approach to this problem.
TIA
   joachim heidemeier

--
Dr. Joachim Heidemeier
c/o Umweltbundesamt FG II 2.2
Tel.: +49340 2103-2780
eMail: joachim.heidemeier@uba.de




	[[alternative HTML version deleted]]