[R-sig-Geo] DELDIR

[PONS Frederic - CEREMA/DTerMed/DREC/SRILH]

Dear all

Sometines we are using the deldir function for squeletisation.

Since the last review, deldir stops in some shapefile because polygons 
are too narrow. In the version berfore, there was no problems.

We have readed the " Notes on error messages" and the problem of 
anticlockwise order of triangle is listed.

In the trifnd R function , the code is
# Check that the vertices of the triangle listed in tau are
# in anticlockwise order.  (If they aren't then alles upgefucken
# ist; throw an error.)
call acchk(tau(1),tau(2),tau(3),anticl,x,y,ntot,eps)
if(!anticl) {
     call acchk(tau(3),tau(2),tau(1),anticl,x,y,ntot,eps)
     if(!anticl) {
         call fexit("Both vertex orderings are clockwise. See help for 
deldir.")
     } else {
         ivtmp  = tau(3)
         tau(3) = tau(1)
         tau(1) = ivtmp
     }
}

We don't understand why do not order the bad triangles into the good 
order. Perhaps, if this problem appears, the beginning of the deldir 
function is not good.

If someone can explain us.

Best regards

*Frédéric Pons
*

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