panel.abline(a, b, ...)
panel.abline(coef, ...)
panel.abline(reg, ...)
panel.abline(h= ,v= , ...)
panel.fill(col="grey", ...)
panel.grid(h=3, v=3, ...)
panel.lmline(x,y,...) = panel.abline(lm(y~x),...)
panel.loess(x, y, span=2/3, iter=3, ...)
panel.mathdensity(dmath = dnorm, args = list(mean=0, sd=1))panel.loess is essentially a wrapper on
    lowessx, e.g., dnormpanel.abline adds a line of the form y=a+bx or vertical
  and/or horizontal lines. Graphical parameters are obtained from 
  reference.line for panel.grid, and add.line for the
  others (can be set using trellis.par.set )  panel.mathdensity plots a (usually theoretical) probability
  density function. Can be useful in conjunction with histogram
  and densityplot to visually estimate goodness of fit.
lowess, trellis.par.get