[R] testing parallelism of does-response curves using package "drc"

[Walmes Zeviani]

Using just nls() you can set the complete model and the alternative model in
this way

da <- expand.grid(x=20:50, trat=c(0.9,1))
da$y <- 10*da$trat*da$x/(12+da$x)+rnorm(da$x,0,0.1)
plot(y~x, da)
da$trat <- as.factor(da$trat)

n0 <- nls(y~A[trat]*x/(B[trat]+x), data=da,
          start=list(A=c(9,10), B=c(12,12)))
n1 <- nls(y~A*x/(B[trat]+x), data=da,
          start=list(A=c(9.5), B=c(12,12)))
anova(n1,n0)

Look at gnls() function in the nlme package for a easier way to specify the
model.

Walmes Zeviani.

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..(....)... 0ooo...                              Walmes Zeviani
...\..(.....(.....)...     Master in Statistics and Agricultural
Experimentation
....\_)..... )../....       walmeszeviani at hotmail.com, Lavras - MG, Brasil
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