[R-sig-Geo] contours in SpatialPixelsDataFrame

[Agustin Lobo]

I have a set of regularly distributed points (a grid) as a SpatialPoints DF.
In order to display the distribution of a continuos varaible in the data table,
I transform to SpatialPixelsDataFrame (using gridded(a) <- TRUE)
and after calculating the dimensions of the grid I use rasterize() to convert
to raster and then use rasterVIS::levelplot()

My question is, can equivalent contours be drawn directely on the
SpatialPixelsDataFrame object
to skip the tansform to raster?
I've tried with spplot(), but get filled intervals, not line contours.

Thanks

Agus