[R] local variance estimation using gam or locfit
Takatsugu Kobayashi
tkobayas at indiana.edu
Tue Feb 12 07:34:41 CET 2008
Hi,
I appreciate if any one could give me clues about the following problem.
I have a map data, x, y, z, and d, where (x,y) is the coordinate of a
point and d is a distance from the urban center (0,0), and z is
population density. Then I would like to calculate local standard
deviations of these points. Let me say hypothetically,
x <- rnorm(100)
y <- rnorm(100)
z <- runif(100)
d <- sqrt(x^2+y^2)*runif(100,1,1.5)
mod <- gam(z~s(x,y,by=d))
std.res.loc <- residuals/loc.std
So, I would like to calculate loc.std. Is there any function available
for this? Or should I manually compute it?
I am reading "Generalized Additive Model: Introduction to R" by Dr. Wood.
Thank you very much.
Tk
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