On Wed, 6 Aug 2003, Ross Ihaka wrote: > Adrian Baddeley wrote: > > Hi, > > > > Sorry if this is already known... > > > > contour() sometimes draws contour lines that intersect. > > Is there a temporary fix? > > > > A dataset which causes problems is at > > http://www.maths.uwa.edu.au/~adrian/dumpdata.R > > If you try just > > source("dumpdata.R") > > image(huh) > > contour(huh) > > the 100 x 100 matrix 'huh' contains an hourglass-shaped region > > of values around 0.8. The contour plot shows two contour lines at > > the level 0.8 which cross each other in a figure 8. > > > > In the short term can anyone suggest how to fix the contour plot > > for this particular dataset?? > > A close look suggests that the lines don't actually cross -- e.g. try > > contour(huh, xlim = c(0.82, 0.88), ylim = c(0.1, 0.12)) > Or even:
contour(huh, levels=seq(0.75, 0.85, 0.001), xlim = c(0.82, 0.88), ylim = c(0.1, 0.12)) - the data are very flat. It does look odd zoomed out, though - maybe avoid the 0.8 contour by setting levels to something other than the default? This looks OK: image(huh, breaks = round(quantile(huh, prob = seq(0,1,0.1)), 2), col = heat.colors(10)) contour(huh, levels = round(quantile(huh, prob = seq(0,1,0.1)), digits = 2), drawlabels=FALSE, add=TRUE) but obviously there are good reasons for the pretty() default levels. filled.contour(huh, color.palette = rainbow, xlim = c(0.82, 0.88), ylim = c(0.1, 0.12)) shows the same effect. > The handling of the "crossing case" in R is an implementation of that in > Cleveland's "Visualizing Data" (one of the "for-the-record" sections). > I don't think the algorithm permits crossings. > > -- Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Breiviksveien 40, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93 e-mail: [EMAIL PROTECTED] ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
