Polygon contains_point() different from matplotlib.nxutils.points_inside_poly?

Reckoner · February 13, 2012, 4:47pm

I'm trying to test whether or not the origin is contained inside the following triangle
inscribed inside a circle:

th = array([ 2.3913423, 5.3133123, 1.8516171])
p=patch.Polygon(array([cos(th),sin(th)]).T)

p.contains_point((0,0))

returns 0

but,

matplotlib.nxutils.points_inside_poly([[0,0]],p.get_path().vertices)

returns True

What am I missing here?

Thanks!

Jerzy_Karczmarczuk · February 13, 2012, 6:25pm

I'm trying to test whether or not the origin is contained inside the
following triangle
inscribed inside a circle:

th = array([ 2.3913423, 5.3133123, 1.8516171])
p=patch.Polygon(array([cos(th),sin(th)]).T)

What do you mean by "patch" here?

I tested

p=Polygon(array([cos(th),sin(th)]).T)
p.contains_point((0,0))

and the answer is 1.

Jerzy Karczmarczuk

···

Le 13/02/2012 17:47, reckoner a écrit :

Reckoner · February 13, 2012, 7:33pm

Here's a better example:

th= array([ 4.65542641, 5.32920696, 2.20928291])
p=patch.Polygon(array([cos(th),sin(th)]).T)
print p.contains_point((0,0))

1

print matplotlib.nxutils.pnpoly(0,0,p.get_path().vertices)

0

Thanks!

···

On 2/13/2012 8:47 AM, reckoner wrote:

I'm trying to test whether or not the origin is contained inside the
following triangle
inscribed inside a circle:

th = array([ 2.3913423, 5.3133123, 1.8516171])
p=patch.Polygon(array([cos(th),sin(th)]).T)

p.contains_point((0,0))

returns 0

but,

matplotlib.nxutils.points_inside_poly([[0,0]],p.get_path().vertices)

returns True

What am I missing here?

Thanks!

Benjamin_Root · February 13, 2012, 7:47pm

I can confirm this for both the current development branch and v1.1.x. Strange…

Ben Root

···

On Mon, Feb 13, 2012 at 1:33 PM, reckoner <reckoner@…287…> wrote:

Here’s a better example:

th= array([ 4.65542641, 5.32920696, 2.20928291])

p=patch.Polygon(array([cos(th),sin(th)]).T)

print p.contains_point((0,0))

1

print matplotlib.nxutils.pnpoly(0,0,p.get_path().vertices)

0

Thanks!

Jerzy_Karczmarczuk · February 13, 2012, 8:59pm

reckoner:

      >>> th= array([ 4.65542641,  5.32920696,

2.20928291])

      >>> p=patch.Polygon(array([cos(th),sin(th)]).T)

      >>> print p.contains_point((0,0))

      1

      >>> print

matplotlib.nxutils.pnpoly(0,0,p.get_path().vertices)

      0



      Thanks!

      I can confirm this for both the current development branch and

v1.1.x. Strange…

      Ben Root

HYPOTHESIS (I have no time to check now everything..., I did my

best.)

If radius=None, it is converted into radius=1 in contains_point (in

Patch).

(This is the linewidth !)

I am not sure whether it is ok, i.e. in pixels. If this value is

considered to be relative to axes, it is enormous!

p.contains_point((0,0),radius=0.01)

gives 0 as it should.

Jerzy Karczmarczuk

P.S. I suggest anyway that reckoner submits a complete program with

imports. What is “patch”??

Benjamin_Root · February 13, 2012, 9:16pm

Jerzy is right. contains() and contains_point() both takes a radius argument as this function is intended for use when mouse-clicking. If no radius is given, it uses the object’s linewidth and passes it to the path’s contains_point() function with its transform. I suspect that the problem is that the transforms haven’t been fully defined yet and might be incorrectly testing this.

This needs a bit more investigation to see if this is the intended behavior or if something needs to be fixed.

As a side note, “patch” is an imported module via “from matplotlib import patches as patch”. Not standard among mpl devs, but not out of the ordinary.