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Re: pde toolbox
Posted:
Mar 15, 2013 11:53 AM


Hi Bill,
Thanks for your reply.
In the pde toolbox, under the 'Boundary' option, I used the export decomposed geometry matrix to get 'g' into my workspace.
You were right about the significant digits. I have fixed the problem. Thank you.
"Bill Greene" wrote in message <khv4r7$ht1$1@newscl01ah.mathworks.com>... > "Sashankh Rao" wrote in message <kht5k2$l97$1@newscl01ah.mathworks.com>... > > Hi, > > > > I create a geometry using the pde toolbox GUI. I then export the decomposed geometry matrix g into the command space. Now I try to use the > > [p,e,t] = initmesh(g) and it works fine. > > > > However, if I copy the same g matrix from the command space to an .m file and try to use initmesh I receive the following error: > >  > > ??? Error using ==> pdevoron at 32 > > Geometry error. > > > > Error in ==> initmesh at 208 > > [p,t,c,h]=pdevoron(p,t,[],h,x,y,tol,Hmax,Hgrad); > > > > Error in ==> mhp at 63 > > [p,e,t] = initmesh(g); > >  > > I examined my geometry and found that there was a gap. Theoretically the two points must overlap since they are the same. Is this a visualization problem or is there really a gap in my boundary? How can I close this gap? Why does it work in the command space but not when I use the matrix in a .m file. Thanks. Below is my geometry matrix: > > > > g =[ > > > > 2 2 2 2 2 2 2 4 > > 1 0 0.2242 0.7154 0 0.0950 0.4698 1 > > 1 0.2242 0.7154 1 0.0950 0.4698 0.8447 0.8447 > > 0 0 0 0 0 0.0950 0.4698 0.4698 > > 0.4698 0 0 0 0.0950 0.4698 0.8447 0.8447 > > 1 1 1 1 0 0 0 1 > > 0 0 0 0 1 1 1 0 > > 0 0 0 0 0 0 0 0.4698 > > 0 0 0 0 0 0 0 0.4698 > > 0 0 0 0 0 0 0 0.5302 > > 0 0 0 0 0 0 0 0.5302 > > 0 0 0 0 0 0 0 0 > > ]; > > > > Thanks, > >  Sai > > > Hi, > > You said above: > >export the decomposed geometry matrix g into the command space. > > How exactly did you do this? pdetool has an option to export gd (geometry > description matrix), ns and sf into the the command space but I'm not > aware of a way to export the decomposed geometry matrix. > > If you export gd, ns, and sf, you can then call decsg to *compute* the > decomposed geometry matrix > > g = decsg(gd, sf, ns); > > Then the g matrix will have full numerical precision so that there are no > gaps between the edges. The reason for the gaps in your > decomposed geometry matrix may be that it is represented only > to four significant digits. If you want to save a text form for > the decomposed geometry matrix (like you show in your post), > print the entries with 16 significant digits. > > Bill



