comp.lang.idl-pvwave archive - RDF feed
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description: Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
items: TRIANGULATE says "Points are co-linear, no solution"
items: Re: TRIANGULATE says "Points are co-linear, no solution"

TRIANGULATE says "Points are co-linear, no solution"
type: item
description: TRIANGULATE says "Points are co-linear, no solution" This really bugs me, because it's just not true. Well, it may be true for a subset of the points I'm trying to triangulate, but certainly not all. Is the IDL triangulate code just really weak? I wish I had an example of this with a small number of points. I thought I should be able to get a triangulation with just about any set of points, except for one in which all of the points lie along the same line. This is certainly not true for my dataset - in fact, I think it looks darned reasonable, and I want to resample onto a regular grid dammit! Anyway, if anyone wants to take a look, Please! The data set is a file called test.dat (saved on hp-ux using writeu. I hope there are no byte swapping problems for other platforms) ftp://scorpio.tn.cornell.edu/jj/idl/ IDL> x=fltarr(9853) IDL> y=fltarr(9853) IDL> openr,unit,'test.dat',/get_lun IDL> readu,unit,x, IDL> triangulate,x,y,tr,b % TRIANGULATE: Points are co-linear, no solution. ;; see the data (doesn't look bad to me) IDL> plot,xx,yy,/device,psym=3 HELP!! Thanks. BTW, this was orignally a double array - that didn't work either. -Jonathan
creator: Jonathan Joseph
date: 1999-11-11T08:00:00-00:00

Re: TRIANGULATE says "Points are co-linear, no solution"
type: item
description: I get the same error running IDL 5.2.1 on Solaris... In article <382C2028.7AD6@scorpio.tn.cornell.edu>, Jonathan Joseph <jj@scorpio.tn.cornell.edu> wrote: > Sorry about the IDL code mixup, some cut/paste > problems - and the fact that I changed variable names from > from xx and yy to x and y (after pasting) but forgot to change > them all. In other words, I noticed that in the code I supplied > that the readu command was missing the "y" at the end of it, and > the plot command was plotting xx and yy instead of x and y > (and probably shouldn't have had the /device on it). And > I left off the "close, unit" command to > clean up the open file unit - though that shouldn't > have mattered. Sorry, I was in a rush and can only > plead incompetancy. > > Anyway, I *AM* running idl 5.2 (well, 5,2,1), so presumably, > I should not have this problem. I have created an IDL save file > now at the same place ftp://scorpio.tn.cornell.edu/jj/idl/ > The file is called test.sav > > The following code should work: > And by that, I mean (not work). > At least, it causes the error listed below on my > system (IDL 5.2.1 running on HP-UX 10.20) > > ;; restore the data > IDL> restore,'test.sav' > ;; create a window > IDL> window > ;; plot the data to see that it looks reasonable > IDL> plot,x,y,psym=3 > ;; try to triangulate the points > IDL> triangulate,x,y,tr,b > % TRIANGULATE: Points are co-linear, no solution. > > I have tried the jitter business before to good effect. > I guess I'll go that route for now, I just didn't want to > accidentally jitter it too much and get "negative triangles" > when I applied the triangulation to the real positions. > > As for what the data is... Well, it has something to do > with stereo offsets between images. The interesting coastline > effect is due to certain (dark) areas of the images are > not being processed - and there is also a polygonal clipping region > applied. The actual images are of asteroid 253 Mathilde. > > And I apologize for the ranti…
creator: cjengo
date: 1999-11-12T08:00:00-00:00