R help - Jan 2009 - plotting points with two colors

Dear Miss R,
    I am trying to plot a scatterplot in which the points (round) should
have two colors: half red and half blue (if you want: two half solid circles
put together. Can you please help me to realize this efficiently?

Thank you,
Best regards, Georg.
***************************************
Georg Ehret
Geneva University Hospital
Geneva, Switzerland

	[[alternative HTML version deleted]]

?plot.default

plot(x <- rnorm(47), type = "p", main = "plot(x, type =
\"p\")", col =
c("dark red","blue"))

If you plan to have a system for the coloring, you need to get the  
values sequence-aligned with the colors. This just colors every other  
point "blue".
-- 
David Winsemius

On Jan 20, 2009, at 12:23 PM, Georg Ehret wrote:
> Dear Miss R,
>    I am trying to plot a scatterplot in which the points (round)  
> should
> have two colors: half red and half blue (if you want: two half solid  
> circles
> put together. Can you please help me to realize this efficiently?
>
> Thank you,
> Best regards, Georg.
> ***************************************
> Georg Ehret
> Geneva University Hospital
> Geneva, Switzerland
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

I don't know how efficient you would consider this, but here is one
solution:

library(TeachingDemos)

ms.2circ <- function(r=1, adj=0, col1='blue', col2='red',
npts=180) {
	tmp1 <- seq( 0,   pi, length.out=npts+1) + adj
	tmp2 <- seq(pi, 2*pi, length.out=npts+1) + adj
	polygon(cos(tmp1)*r,sin(tmp1)*r, border=NA, col=col1)
	polygon(cos(tmp2)*r,sin(tmp2)*r, border=NA, col=col2)
	invisible(NULL)
}

x <- runif(10)
y <- rnorm(10)
a <- runif(10, 0, 2*pi)

my.symbols(x,y, ms.2circ, inches=0.15, add=FALSE, symb.plots=TRUE, adj=a)

# or

my.symbols(x,y, ms.2circ, inches=0.15, add=FALSE, symb.plots=TRUE, adj=a,
	col1="#00ff0088", col2="#ff00ff88")

Hope this helps,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Georg Ehret
> Sent: Tuesday, January 20, 2009 10:23 AM
> To: r-help
> Subject: [R] plotting points with two colors
> 
> Dear Miss R,
>     I am trying to plot a scatterplot in which the points (round)
> should
> have two colors: half red and half blue (if you want: two half solid
> circles
> put together. Can you please help me to realize this efficiently?
> 
> Thank you,
> Best regards, Georg.
> ***************************************
> Georg Ehret
> Geneva University Hospital
> Geneva, Switzerland
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.