R- Users:

Can someone indicate what I am during wrong? This is a script essentially from 

Venerable & Ripley's text on interpolating a surface with loess function but I can not get it to run.

Thanks.

John Lewis

Professor

McGill University

Montreal



library(MASS)

library(modreg)

data(topo)

par(mfcol=c(2,2), pty="s")

topo.loess <- loess(z ~ x * y, topo, degree=2, span = 0.25, normalize=F)

topo.mar <- list(x = seq(0, 6.5, 0.1), y=seq(0, 6.5, 0.1))

topo.lo <- predict(topo.loess, expand.grid(topo.mar), se=T)

lo.1 <- as.data.frame(topo.lo)

lo.2 <- as.matrix(lo.1$fit)

lo.3 <- as.matrix(lo.1$se.fit)

contour(topo.mar$x,topo.mar$y,lo.2, levels = seq(700,1000,25),

        xlab="fit", ylab="")

points(topo)

contour(topo.mar$x,topo.mar$y,lo.3, levels = seq(5, 25, 5),

        xlab="standard error", ylab="")

title("Loess degree = 2")

points(topo)


This is the error I keep getting.

"Error in contour.default(topo.mar$x, topo.mar$y, lo.2, levels = seq(700,  : 
        no proper `z' matrix specified" 

I received this same message when I ran the script first without changing topo.lo
from a list to data.frame etc. as seen below.

contour(topo.mar$x,topo.mar$y,topo.lo$fit, levels = seq(700,1000,25),

        xlab="fit", ylab="")


I checked the length of each variable and they are correct.
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