[R] Intercept=0 in gam from gam package

[Gavin Simpson]

On Thu, 2009-09-10 at 14:58 +0100, Corrado wrote:
> Dear R list,
> 
> is it possible to force the intercept to assume the value of 0 (that is no 
> intercept) in gam from gam package?

Just like you would in lm or glm for example, by adding -1 to your
formula. ?gam suggests you look at ?lm to see about the formulas for
example.

data(airquality)
mod0 <- gam(Ozone^(1/3) ~ lo(Solar.R) + lo(Wind, Temp) - 1, 
            data = airquality, na = na.gam.replace)
mod1 <- gam(Ozone^(1/3) ~ lo(Solar.R) + lo(Wind, Temp), 
            data = airquality, na = na.gam.replace)

summary(mod0)
summary(mod1)

HTH

G

> 
> Regards
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