Plotting curves in lattice panels

On 9/18/08, David Scott <d.scott at auckland.ac.nz> wrote:

 I have a data set concerning ferritin levels in blood. There are three
relevant columns for this question, ferritin (continuous), score (ordered,
from 0 to 8) and gender. There is a good linear relationship between
log(ferritin) and score for each gender.

 I can create a lattice plot on the log scale showing the data and the
fitted line:
 xyplot(log(ferritin)  ~ total|gender, data = blood,
       panel = function(x, y, ...){
         panel.xyplot(x, y)
         panel.abline(lm(y ~ x), type = 'l', ...)
       }
 )

 I would like to be able to plot the data and the fitted line on the
original scale however. I can't see how to do that.

Something like this should work:

xyplot(ferritin  ~ total|gender, data = blood,
      panel = function(x, y, ...){
          panel.xyplot(x, y)
          fm <- lm(log(y) ~ x)
          panel.curve(exp(predict(fm, newdata = list(x = x))))
      })

-Deepayan