[R] Use of colour in plots

Greg Snow Greg.Snow at imail.org
Thu Sep 18 18:56:05 CEST 2008

Try something like:

> x <- runif(25)
> y <- rnorm(25)
> z <- rnorm(25, 3*x)
> plot(x, y, col=ifelse( z > 1.25, 'red', 'green') )

Does this help,

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

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Steve Murray
> Sent: Thursday, September 18, 2008 8:14 AM
> To: ONKELINX, Thierry; Petr PIKAL; jrkrideau at yahoo.ca;
> jim at bitwrit.com.au
> Cc: r-help at r-project.org
> Subject: Re: [R] Use of colour in plots
> Jim and all,
> Maybe I've misunderstood ?color.scale (appologies if this is so), but I
> don't think this is what I need. I'm not looking to scale the colours
> of points, instead I simply want to assign each point a colour (either
> red or green) based on it's value in the Urban.Rural column.
> To clarify (but please also see my earlier message if this helps):
> In my dataset (Jan) I have 3 columns of interest: Average Burnt Area
> Fraction (ABAF), PopDensity and Urban.Rural.
> I want to plot ABAF against PopDens (which I've had no problems doing)
> and then, regardless of the values of ABAF and PopDens, I want to
> assign it a colour. The colour each point is given is based on the
> corresponding Urban.Rural value on each row. If for each pair of ABAF
> and PopDens values the Urban.Rural value on that row is>1.25, then the
> point should be coloured red, whereas if it's =
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