Another alternative is to use SSlogis which is very similar to the
model you're fitting except with one additional parameter:
Asym <- 3
xmid <- 0
scal <- 10
model <- nls(bod ~ SSlogis(time, Asym, xmid, scal), data = mydata)
summary(model)
plot(bod ~ time, mydata)
newdata <- data.frame(time = seq(1
Hi, Michael,
I think the SPSS answer is wrong. Your starting values are way off.
Look at this plot for verification:
con <- textConnection("time bod
11 0.47
22 0.74
33 1.17
44 1.42
55 1.60
67 1.84
79 2.19
8 11 2.17")
mydata <- read.table(con, header = TRUE)
close(co
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