Hi Steve, I don't know how large is your data, but I think usually alpha-transparency can solve the problem of overplotting, if small points won't work. For example, you can specify alpha = 0.1 in rgb() to generate transparent colors and plot your data points. You may take a look at the example 1 in: http://www.yihui.name/en/post/51.htm
Regards, Yihui -- Yihui Xie <[EMAIL PROTECTED]> Phone: +86-(0)10-82509086 Fax: +86-(0)10-82509086 Mobile: +86-15810805877 Homepage: http://www.yihui.name School of Statistics, Room 1037, Mingde Main Building, Renmin University of China, Beijing, 100872, China On Fri, Sep 19, 2008 at 3:02 AM, Steve Murray <[EMAIL PROTECTED]> wrote: > > Greg, > > Thanks for this - it works really well! > > One (hopefully final!) question I have is, is there any way of preventing > overplotting? I'm finding that many of the red points are being obscured by > the greens - I've tried making the point sizes small (cex=0.1) but this > doesn't fully solve the problem. > > Or even, is there a way of changing the order of which the points are plotted? > > Thanks again, > > Steve > > > > >> From: [EMAIL PROTECTED] >> To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL >> PROTECTED]; [EMAIL PROTECTED] >> CC: [email protected] >> Date: Thu, 18 Sep 2008 10:56:05 -0600 >> Subject: RE: [R] Use of colour in plots >> >> 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 >> [EMAIL PROTECTED] >> 801.408.8111 >> >> >>> -----Original Message----- >>> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] >>> project.org] On Behalf Of Steve Murray >>> Sent: Thursday, September 18, 2008 8:14 AM >>> To: ONKELINX, Thierry; Petr PIKAL; [EMAIL PROTECTED]; >>> [EMAIL PROTECTED] >>> Cc: [email protected] >>> 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 = >>> >>> ______________________________________________ >>> [email protected] 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. > > _________________________________________________________________ > Discover Bird's Eye View now with Multimap from Live Search > > ______________________________________________ > [email protected] 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. > ______________________________________________ [email protected] 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.
