[R] contour lines intersect
ihaka at r-project.org
Wed Aug 6 10:00:36 CEST 2003
Adrian Baddeley wrote:
> 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
> If you try just
> 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))
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.
Ross Ihaka Email: ihaka at r-project.org
The R Project and R Foundation
More information about the R-help