Problem using minboundquad function to create a minimum bounding quadrilateral for a given pointset

I had modified one line in the minboundquad.m function to remove the collinear edges in the pointset.

from

edges = convhull(x,y);

to

edges = convhull(x,y,'Simplify',true);

The main code is

load points2.txt
x = points2(:,1);
y = points2(:,2);
[qx,qy] = minboundquad(x,y)

Result I got is below.

There is some error I could not find out. Can someone help me solve this?

Answer 1

[Gowtham HariHara]

Modifying the line in minboundquad.m from

if ( A_i < quadarea)

to

if (( A_i < quadarea)&& all(abs([qxi qyi]) < 1e15))

resolves the issue.

Thanks to @Michael Sapper for this suggestion(found in comment section of this toolbox)

Answer 2

[Shiva Kalyan Diwakaruni]

Hi,

I did not seem to find any error while reproducing and I got the below result after changing minboundquad.m

from

edges = convhull(x,y);

to

edges = convhull(x,y,'Simplify',true);

I got the Warning: Matrix is close to singular or badly scaled. Results may be inaccurate.

Can You explain what your error was?

[Gowtham HariHara]

@Shiva Kalyan Diwakaruni Thank you for your time.

There is no quadrilateral formed. Outcome of this function should be four vertices of a quadrilateral.

[Gowtham HariHara]

@Shiva Kalyan Diwakaruni Do you want to see the expected outcome of this function ?

This function worked for one of the less complex pointset. If you would like to see the result for a working pointset, I can show a screenshot.