Hi,
When very simple models are tested in step.gam, I have observed the some
difference in the final output result based upon the version of the
package tested. Is this an expected behavior or a bug in the latest
version of the gam package?
With gam 1.4:
> data(gam.data)
> gam.object <- gam(y~1, data=gam.data)
> step.object <- step.gam(gam.object, scope=list(x=c('1','x')))
Start: y ~ 1; AIC= 232.8823
Trial: y ~ x; AIC= 126.5148
Step : y ~ x ; AIC= 126.5148
> step.object
Call:
gam(formula = y ~ x, data = gam.data, trace = FALSE)
Degrees of Freedom: 99 total; 98 Residual
Residual Deviance: 19.53955
With gam 1.9.1 or 1.12:
> data(gam.data)
> gam.object <- gam(y~1, data=gam.data)
> step.object <- step.gam(gam.object, scope=list(x=c('1','x')))
Start: y ~ 1; AIC= 232.8823
Step:1 y ~ x ; AIC= 126.5148
> step.object
NULL
Thank you
Sebastien
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