R help - Dec 2013 - plot() function: color transparency

I found all the color transparency was defined with character color, or rgb
color. What if I have number code and still try to modify the transparency?

For example:
>x=c(1:5)
> color=c(2,2,3,4,5)
> plot(x, col=color)
> plot(x, col=color,pch=20)
here I defined color by numbers, how can I modify the transparency?

Thanks a lot for any input!

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On 13-12-18 2:08 PM, capricy gao wrote:
> I found all the color transparency was defined with character color, or rgb
color. What if I have number code and still try to modify the transparency?
>
> For example:
>
>> x=c(1:5)
>> color=c(2,2,3,4,5)
>> plot(x, col=color)
>> plot(x, col=color,pch=20)
>
> here I defined color by numbers, how can I modify the transparency?
See the examples for ?palette.

Duncan Murdoch