On Tue, 2 Feb 2010, Paulo Eduardo Cardoso wrote:
Hi,
A good work around for representation but not exactly what was
expected for the real dataset.
The image with alpha channel (transparency) is just a schema to
provide the idea of hidden points but they are not supposed to be
visible. Sorry.
Considering that all points are plotted at first, wihout using
"in-out", is there a way to overlap areas[1,] keeping "in" points
visible?
No, because the enclosing square overpaints them, and the hole is painted
on top of that - that is the graphics model. The only way round would be
(as old plotter-based representations) to make returning lines in to the
hole and back out to the perimeter, so that the hole would be "outside"
the square. This has been dropped everywhere because of the difficulty of
hiding the "moorings". If you want to show the points in the hole in
areas[1,], you have to paint areas[1,] first, then the points in the hole.
In general terms:
plot(areas[1,], pbg="white", col="grey85", border="grey50")
o <- overlay(pontos, areas[1,])
points(pontos[is.na(o),], pch=16)
shows the points in the hole, but you can't use a polygon with an
un-"moored" hole as a mask.
Roger
Paulo
2010/2/2 Roger Bivand <roger.biv...@nhh.no>:
On Mon, 1 Feb 2010, Paulo Eduardo Cardoso wrote:
Hi,
Code exemple
library(maptools)
load(file='D:\\R\\transparencia\\TransparentPolygon.Rdata')
areas <- readShapeSpatial('D:\\R\\transparencia\\Areas.shp')
pontos <- readShapeSpatial('D:\\R\\transparencia\\Points.shp')
plot(pontos,pch=19,col=pontos$point)
plot(areas,pbg="transparent",bg="red",add=TRUE)
data can be downloaded from
http://rapidshare.com/files/344532718/TransparentPolygon.Rdata.html
example image can be downloaded grom
http://rapidshare.com/files/344533300/ExampleTransparentPolygon.png.html
The image cannot be reproduced with your plotting order, because the
polygons overpaint the points. Crucially, the big square is completely
painted. You also have two Polygons objects, one a square with a round hole,
the other an island filling the hole. With your objects, you could do:
plot(areas[1,], pbg="white", col="grey85", border="grey50") # set up
background polygon and paint hole
plot(areas[2,], angle=45, density=8, border="grey50", col="grey50",
add=TRUE)
# hatch the island polygon
points(pontos[pontos$point=="in",], pch=16)
# add the in points
points(pontos[pontos$point=="out",], pch=22, col="grey50", bg="grey50")
# and the out points
If your output devive uses and alpha channel, you may be able to find other
ways forward, but they will not be portable across devices.
Hope this helps,
Roger
2010/1/31 Roger Bivand <roger.biv...@nhh.no>
On Sun, 31 Jan 2010, Paulo Eduardo Cardoso wrote:
Roger,
I really thank you for you comments. You are always available to explain
everything, and that's a fortune for forum users.
But I still with the same problem. I did,'t understand how to leave the
inner hole or the inner polygon transparent, in order to see any other
layer
plotter at first.
Should I send a simple example?
Please do, either code for a provided data set, or code and a link to the
URL where the data set is available.
Roger
2010/1/30 Roger Bivand <roger.biv...@nhh.no>
On Sat, 30 Jan 2010, Paulo Eduardo Cardoso wrote:
I'd like to plot a SPDF with two objects, one of them buffering the
other
"island". How can I set the "island" transparent?
Similarly, keeping the outer polygon only, how can the hole still
transparent?
Polygons objects are plotted largest to smallest, as are Polygon
objects in
each Polygons object. Each Polygons object and all its constituent
Polygon
objects are painted the colour chosen for that Polygons object.
If you want the holes Polygon objects to overpaint their containing
Polygon
objects, in the base graphics plot() method, you set the pbg= argument
to
the background colour (not "transparent", this will let you see the
painted
Polygon below). In the spplot method, this is handled internally by
reading
the trellis.par.get()$background value, and using it if not
"transparent",
or "white" if it is "transparent".
Both approaches depend on the hole slot of the Polygon object being
correctly set.
R graphics do not analyse objects leaving out say holes, they
overpaint.
This is because the holes are not "known" in advance by the functions
being
executed.
Hope this helps,
Roger
Thanks in advance,
Paulo E. Cardoso
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Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School
of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
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e-mail: roger.biv...@nhh.no
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
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