[R] transparency using plot+points with sp classes

Jeff Newmiller jdnewmil at dcn.davis.ca.us
Wed Dec 28 19:09:10 CET 2011

Some output devices don't support transparency. Try a different output device.
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Ana <rrasterr at gmail.com> wrote:

>Hi guys,
>Thansk for the help with the transparency.
>I've made some modifications to my code , added rgb in colour to play
>with the transparency and included also a north arrow. I was trying to
>make the code look better, however i am facing another problem, once I
>use symbols with a bg colour. Somehow once I plot the map I loose the
>bg colour info and he gives me only the filled triangle border colour:
>arrow <- list("SpatialPolygonsRescale", layout.north.arrow(type=1),
>offset = c(5,10), scale = 2,col="black")
>list1=list("sp.points",observations2000,pch=21,col = rgb(red = 0,
>green = 0, blue = 1, alpha = 0.1))
>       sp.layout=list(arrow,list1,list2,list3),
>  scales=list(draw=TRUE),xlab="Longitude",ylab="Latitude", main="Map" )
>On Wed, Dec 28, 2011 at 1:13 PM, Ana <rrasterr at gmail.com> wrote:
>> How can I make one point graphics with transparency
>> These are all sp classes:
>> plot(polygons_area,axes=TRUE,asp=1.5,main="Title",xlab="Latitude",
>> ylab="Longitude")
>> points(observations2000,type = "p",pch=21,col="green")
>> points(observation1999,type = "p",pch=21,col="blue")
>> points(reference.points,type = "p",pch=21,col="red")
>> how can I add transparency to one of the point graphics, for example
>> points(observation1999,type = "p",pch=21,col="blue")  ?
>R-help at r-project.org mailing list
>PLEASE do read the posting guide
>and provide commented, minimal, self-contained, reproducible code.

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