interpolation using akima (PR#8174)
Please do read the posting guide and FAQ, as we do ask you to do before sending a bug report. 1) Your version of R is not current. 2) akima is a contributed package and you are not the maintainer. We do ask you not to `behave in this manner'.
On Mon, 3 Oct 2005 jonathan_lees at unc.edu wrote:
Full_Name: Jonathan Lees Version: 2.0.1 OS: linux-gnu Submission from: (NULL) (152.2.75.65) there is a problem with calculating the convex hull in 2-D interpolation using the codes interp fromt eh akima package: x =c(0.6505304, -1.1821562, -0.2600792, 0.7913716) y = c(1.0424226, 0.1754048, -1.4523334, 0.2349112) z = c(0.000, 3.042, 0.370, 0.122) EX = seq(from=min(x), to=max(x), length=100) WHY = seq(from=min(y), to=max(y), length=100) ZZ = interp(x=x, y=y, z=z, xo=EX, yo=WHY, extrap=FALSE) plot(x,y, type='n') image(ZZ, add=TRUE) points(x,y) text(x,y,labels=z) BUG: Notice the convex hull is wrong. It includes only 3 of the 4 points provided. If you add another point near by it does some really wierd stuff. x = c(x, -0.3950865) y = c(y, -1.449117) z = c(z, .37) I do not think it should behave in this manner.
Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595