plot.polylist without borders or controlling the border width

Hi there,

With plot.polylist is there a way of not drawing the "border" or 
controlling the width of the border in order to diminish the vision of 
horror when using a smaller colour range  than the number of polygons 
and when you have quite a lot of polygons in your "shape".

I am thinking as well of possible merging or fusion of neighbour 
polygons having the same color which would give an half way solution ... 
but I don't know the "union" polygon merging polygons function. (which 
should be standard I suppose ...)

thanks

Didier

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