[R] adding regression curve to xyplot

[Deepayan Sarkar]

On Tuesday 30 November 2004 10:09, Carlisle Thacker wrote:
> Dear R-listers,
>
> It seems that predict() behaves differently within panel.xyplot.  Am
> I doing something stupid?
>
> Thanks,
>
> Carlisle
>
> First, without xyplot():
> > lmtest <- lm(t~s,data=subset(P100,whichLon100==1 & whichLat100==1))
> > lmtest
>
> Call:
> lm(formula = s ~ t, data = subset(P100, whichLon100 == 1 &
> whichLat100 == 1))
>
> Coefficients:
> (Intercept)            t
>     33.3307       0.1393
>
> > range(P100$t)
>
> [1]  4.050469 24.514543
>
> >> predict(lmtest,newdata=data.frame(t=range(P100$t)))
>
>        1        2
> 33.89501 36.74620
>
> As expected, predict gives two values.  But inside xyplot() predict
> gives
>
> 300 values:
> > xyplot(t~s|factor(lonLabels[whichLon100])*factor(latLabels[whichLat
> >100]),
>
> +   data=P100,pch=".",
> +   panel=function(x,y,...){panel.xyplot(x,y,...)
> +                           thislm <- lm(x~y)
> +                      print(thislm)
> +                           newt <- range(P100$t)
> +                      print(newt)
> +                           news <-
> as.vector(predict(thislm,newdata=data.frame(t=newt)))

Why 't' here? The variables involved in 'thislm' are 'x' and 'y'.

Deepayan

> +                      print(news)
> +                           llines(news,newt,col="red")})

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