[R] several regression lines in panel of xyplot (trellis graphics)

[Douglas Bates]

Wladimir Eremeev <wl at eimb.ru> writes:

> Dear r-help,
> 
>   I need to draw xyplot() graphs with several regression lines:
>   one line for the whole range of x (the variable on the horizontal
>   axis) and two additional lines for subranges of x.
>   
>   Is it possible to make first regression line (panel.lmline(x,y,...);)
>   to be drawn on the whole graph
>   and regression lines of the subsets to be drawn only over their subsets?
> 
>   I have defined
> plot.panel=function(x,y,...){
>   panel.xyplot(x,y,...);
>   panel.lmline(x,y,...);
>   panel.lmline(x[1:9],y[1:9],...);
>   panel.lmline(x[10:23],y[10:23],...);
>   panel.grid(h=-1,v=-1,...);
> };
> 
> then I draw plots:
>   xyplot(<blah-blah-blah>,panel=plot.panel,<...>)
> 
>   This command draws graphics, but all regression lines on them are
>   drawn from the left side to the right side, i.e. over the whole x
>   range...

I think you will need to do the linear model fits to the data subsets
within the panel function then use panel.segments to add the lines.