[S] nls question

Timothy Johnson (tjohnson@s.psych.uiuc.edu)
Wed, 4 Mar 1998 12:51:31 -0600 (CST)


I'm having some problem using deriv3 with nls. What I am trying to do
is almost exactly like the example in section 9.5 of V&R (2nd ed.).
Here is my code:

my.panel <- function(x,y) {

expn3 <- deriv3(~ b0 - b1 * exp(-b2*x^b3),
c("b0","b1","b2","b3"),
function(x,b0,b1,b2,b3) {})
param <- nls(y ~ expn3(x,b0,b1,b2,b3), start = c(b0 = 1, b1 =
1, b2 = 1, b3 = 1),
data = data.frame(x = x, y = y))$parameters
x.temp <- seq(min(x), max(x), length = 40)
y.temp <- param[1] - param[2] * exp(-param[3]*x.temp^param[4])
lines(x.temp, y.temp)
}

xyplot(cpdiff~groupsize | sim, data = csim,panel = function(x,y,...)
{panel.xyplot(x,y,cex=.60); my.panel(x,y)},
strip=function(...) strip.default(...,strip.name=c(T,T)))

The error I get is this:

Error in nls(y ~ expn3(x, b0, b1, b2, b3), start = c(b0 =..: couldn't
find function "expn3"
Dumped

Any ideas? I'm running version 4.0 on Windows95.

Thanks in advance.

Tim
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