[R] creating a grid of function values
Douglas Bates
bates at stat.wisc.edu
Thu Feb 10 21:28:49 CET 2000
I want to create a grid of function values for use in `contour' or
`persp'. The function is the log-likelihood for the gamma. The
sample is stored as vector of length 20 called `Survival'.
A single evaluation of the log-likelihood at, say, scale = 9 and shape
= 10 would be obtained by
sum(dgamma(Survival, scale = 9, shape = 10, log = TRUE))
(This may work only 0.99.0, I'm not sure.)
I would like to evaluate such a function on a grid of scale and shape
values. I don't think I can use `outer' because of the way the
evaluation of the dgamma function would vectorize. Although I could
write the calculation for the grid in `for' loops, I have a nagging
suspicion that there is a cleaner way that I have forgotten.
Can anyone remind me of a slick way of generating the grid?
--
Douglas Bates bates at stat.wisc.edu
Statistics Department 608/262-2598
University of Wisconsin - Madison http://www.stat.wisc.edu/~bates/
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