Hello all,

I want to draw a grid behind my graphes, using lattice package.
I manage to do it with instructions like this one :

xyplot(Sepal.Length + Sepal.Width ~ Petal.Length ,
       data = iris, allow.multiple = TRUE, scales = "same",type="l",
       panel = function(...) {  panel.grid(h=-1, v= -1) ;
panel.superpose(...)
}
)

I was wondering if there were a way to do it using for example
trellis.par.set() to set this by default, like what I do for colors e.g. :
trellis.par.set(list(superpose.line = list(col = c( "red", "yellow",
"green", "blue", "purple", "orange", "black", "maroon", "pink", "cyan",
"grey", "magenta"  ))))

instead of using in each call this log panel = function (...) { }
instruction

I tried emprirically
 trellis.par.set(list(grid.pars= list(h = -1, v=-1)))

with no success (I am not even sure that this grid.pars is about drawing
grids ... but it is the nearest instruction i found in trellis parameters

As i am not very confident with this trellis.par.set(), I might have missed
something ... I also tried to define a function

grid<-function(...) {  panel.grid(h=-1, v= -1) ;  panel.superpose(...)   }

xyplot(Sepal.Length + Sepal.Width ~ Petal.Length ,
       data = iris, allow.multiple = TRUE, scales = "same",type="l",
       panel = grid()   #also tried grid(...)
)

but the only result is an arror message
with grid() : " Erreur dans unit(y0, default.units) : 'x' et 'units' doivent
avoir une longueur positive " (x and units should have a positive length)
with grid(...) : " '...' utilisé dans un contexte incorrect " ('...' used in
a wrong context)

Could anyone tell me a way of doing it ?





-- 
Pascal Boisson
hoothootprod@gmail.com
http://pak.enroweb.com
http://www.flickr.com/photos/hoothootprod/

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