(no subject)

Le 28 sept. 06 ? 16:18, Roger Bivand a ?crit :

If you say ls(), do the names of any of the objects begin with plot?

ls(pat="plot")

[1] "BBplot"             "Bplot"              "draw.plotmath.cell"
[4] "plot"               "plotG"              "plotM"
[7] "plotx"              "plotxx"

plotx, plotxx, plotG and plotM are functions of mine. Is there a
problem ?

The problem is that your local function plot is masking the one which
understands that "SpatialPolygons" objects have their own method  
and need
to be sent there, so yes, at least your local plot is the problem. The
standard advice if you have a number of functions is to write a  
package
with a NAMESPACE, and that will protect you from R not choosing the  
one
you intended.

Why would be my function plot local ? It is not.
I removed the others

============
 > plot
function (x, y, ...)
{
     if (is.null(attr(x, "class")) && is.function(x)) {
         nms <- names(list(...))
         if (missing(y))
             y <- {
                 if (!"from" %in% nms)
                   0
                 else if (!"to" %in% nms)
                   1
                 else if (!"xlim" %in% nms)
                   NULL
             }
         if ("ylab" %in% nms)
             plot.function(x, y, ...)
         else plot.function(x, y, ylab = paste(deparse(substitute(x)),
             "(x)"), ...)
     }
     else UseMethod("plot")
}
<environment: namespace:graphics>

=============================

Jacques Vernin