[Pkg-octave-devel] Bug in shapecentroid [was: Status of the Octave-Forge packages in Debian]

[Rafael Laboissiere <rafael@laboissiere.net>]

* Rafael Laboissiere <rafael@laboissiere.net> [2012-03-18 20:16]:

> 3) The test of shapetransform fails:
> 
>      ==============================================================
>       ***** test
>      v = shapecentroid (shape)(:);
>      nshape = shapetransform (shape, -v);
>      vn = shapecentroid (nshape)(:);
>      assert(vn,[0; 0],1e-2);
>      !!!!! test failed
>      assert (vn,[0; 0],1e-2) expected
>        0
>        0
>      but got
>        -682.75
>        -528.18
>      maximum absolute error 682.753 exceeds tolerance 0.01
>      ==============================================================

I tracked down the problem and discovered that it comes from the 
shapecentroid function, which seems to compute the wrong centroid in some
cases. Here is an example, with the following shape taken from the test
section of file shapetransform.m:

############################################################
shape = {[-93.172   606.368  -476.054   291.429;
          -431.196   637.253    11.085   163.791];
         [-75.3626  -253.2337   457.1678   328.5714;
          438.7659  -653.6278    -7.9953   380.9336];
         [-89.5841   344.9716  -275.3876   457.1429;
          -170.3613   237.8858     1.0469   158.0765];...
         [32.900  -298.704   145.804   437.143;
         -243.903   369.597   -34.265   226.648];
         [-99.081   409.127  -352.903   317.143;
           55.289  -114.223   -26.781   318.076];
         [-342.231   191.266   168.108   274.286;
           58.870   -38.083   -89.358   232.362]};	
############################################################

Using "shapeplot(shape)", I can clearly see that the centroid for this
shape is situated around x = 340 and y = 260.  However, shapecentroid
gives the following:

############################################################
octave> shapecentroid(shape)
ans =

  -341.38  -264.10
############################################################

The values are negated.

Any clues?

Rafael