plot gam object

Dear R help,

I am fitting a gam model with package GAM ( I use lo() to fit 2 non-parametric 
additive components).

When I plot the GAM object, along with the graphics window displaying plots of 
each components, I read the following warnings at the prompt: 
3: the condition has length 1 and only the first element will be used in: if 
(scale2 < scale) rep(mean(ylim), 2) + ((ylim - mean(ylim)) *  
4: number of items to replace is not a multiple of replacement length .

I am changing the scale parameter but I still get the same warnings. 

I have no idea of the meaning of the warnings, I would be grateful if you could 
help.

Is it possible to find a C code of th ebackfitting algorithm?

Many thanks,

Chiara

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Chiara Peroni
University of York & Bologna