S4 method execution time

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Hello:

I have written some an elementary S4 classes around a matrix to strengthen
control of some key attributes. When I run a fairly elementary function
("f") on the matrix outside the class it runs instantaneously (elapsed
system.time = 0) but when I setMethod "f" on myClass -- returning an
instance of myClass -- it runs perceptibly slower (elapsed system.time =
.06). I suspect my initialization and/or validity functions are
inefficiently written. I thought I read in this list of a function that will
trace the execution time of each of the functions called during the
evaluation of an R expression, but now I can't find that message. Is there
such a function, or was I mistaken?
Maybe Rprof?   That is certainly the tool I would use, and it is 
described in 'Writing R Extensions'.

But we do know that S4 methods do have a significant overhead: OTOH 
there is caching going on and so a lot of this overhead is on first 
use.  So you may find that your 'toy' test does not scale to a real 
problem (surely you have difficulty perceiving 60ms, literally the 
blink of an eye?).
Thank you.

Dan Murphy

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Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
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