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exp2
2002 Mar 19
0
MASS Book Exercise
...;- cbind(1, temp, derive.negexp)
dimnames(Z) <- list(NULL, c("b0","b1","th"))
attr(model.func, "gradient") <- Z
model.func
}
wtloss.gr <- nls(Weight ~ expn(b0, b1, th, Days),
data = wtloss, start = wtloss.st, trace = F)
expn2 <- deriv(~b0 + b1*((w0 - b0)/b1)^(x/d0),
c("b0","b1","d0"), function(b0, b1, d0, x, w0) {})
wtloss.init <- function(obj, w0) {
p <- coef(obj)
# Modified d0 for neg exp model
d0 <- - log((w0 - p["b0"])/p["b1"]) * p[...