-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 15/09/10 15:23, David Winsemius wrote: > > On Sep 15, 2010, at 8:58 AM, Rainer M Krug wrote: > >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA1 >> >> On 15/09/10 14:46, Michael Bedward wrote: >>> Nice posts David. I like the way that 'simple' problems such as this >>> one give rise to an interesting assortment of approaches and gotchas >>> :) >>> >>> Michael >>> >>> On 15 September 2010 22:41, David Winsemius <dwinsem...@comcast.net> >>> wrote: >>>> >>>> On Sep 15, 2010, at 7:55 AM, David Winsemius wrote: >>>> >>>>> >>>>> On Sep 15, 2010, at 7:24 AM, David Winsemius wrote: >>>>> >>>>>> Replacing context: >>>>>> >>>>>>>> Hello everyone. >>>>>>>> I have created a 100*100 matrix in R. >>>>>>>> Let's now say that I have a line that starts from (2,3) point >>>>>>>> and ends >>>>>>>> to the >>>>>>>> (62,34) point. In other words this line starts at cell (2,3) and >>>>>>>> ends >>>>>>>> at cell >>>>>>>> (62,34). >>>>>>>> >>>>>>>> Is it possible to get by some R function all the matrix's cells >>>>>>>> that >>>>>>>> this line >>>>>>>> transverses? >> >> This is a known problem in computer graphics and the algorythm used to >> identify these cells is the "Bresenham's Line Drawing Algorithm" >> >> You can check out one version at >> >> http://www.falloutsoftware.com/tutorials/dd/dd4.htm >> >> or >> >> http://en.wikipedia.org/wiki/Bresenham's_line_algorithm > > After viewing the Wikipedia description and the illustration I think > that may not be the same problem. Note that the cells traversed only at > their very outer corners do not get chosen. The goal is to "approximate > a line" rather than to enumerate traversals.
You might actually be right. Cheers, Rainer > - -- Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology, UCT), Dipl. Phys. (Germany) Centre of Excellence for Invasion Biology Natural Sciences Building Office Suite 2039 Stellenbosch University Main Campus, Merriman Avenue Stellenbosch South Africa Tel: +33 - (0)9 53 10 27 44 Cell: +27 - (0)8 39 47 90 42 Fax (SA): +27 - (0)8 65 16 27 82 Fax (D) : +49 - (0)3 21 21 25 22 44 Fax (FR): +33 - (0)9 58 10 27 44 email: rai...@krugs.de Skype: RMkrug -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkyQyl8ACgkQoYgNqgF2egpdnACfS3zQX3MUAPraxIm5ExbFcnQu bdYAn0vpYs3Gy2XmutNoJQKaVVZ+hnYH =ByN/ -----END PGP SIGNATURE----- ______________________________________________ R-help@r-project.org 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.
