[R] logit GLM without intercept

gorgasal at gmx.de gorgasal at gmx.de
Tue Apr 22 17:04:24 CEST 2008

Hi Robert,

you can exclude the intercept by including "-1" in the formula:

value <- as.numeric(runif(20)<.4)
ppm <- rnorm(20)


> Dear Statisticians,
> I would like to analyse my data with a GLM with binomial error distribution
> and logit link function. The point is that I want a model fitted without
> intercept, i.e. the fitted curve should start at y=0.5 for x=0. 
> I tried it with the following code: 
> glm(value~0+ppm, binomial)
> Does this code yield the correct model or is there another possibility? I?d
> appreciate it very much if you could help me out with this. I attached some
> example data.
> Thanks & all the best
>    Robert


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