[R-sig-Geo] transparency using plot+points with sp classes

[Ana]

Thanks Roman!


Is there a way to move all points of a point graphics
up/down/left/right in reference to the previous position, by a certain
amount of values? This is to avoid overlaps with other point data.


On Wed, Dec 28, 2011 at 1:35 PM, Roman Luštrik <roman.lustrik at gmail.com> wrote:
> You can use ?rgb
>
> plot(0, 0, xlim = c(0, 1), ylim = c(0, 1), type = "n")
> sapply(seq(1, 0, -0.1), function(x)
> points(x = runif(100), y = rep(x, 100),
> col = rgb(red = 0, green = 0, blue = 1, alpha = x), pch = 16))
>
>
> HTH,
> Roman
>
>
>
>
> On Wed, Dec 28, 2011 at 1:14 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")  ?
>>
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>
>
>
>
> --
> In God we trust, all others bring data.