Hi! Bumping this upstream from Sage, where we use quiver to draw

slope fields. The following code

## ···

###

import matplotlib.pyplot as plt

import numpy as np

fig = plt.figure()

r = np.arange(10)

X,Y = np.meshgrid(r,r)

U, V = np.cos(X), np.sin(Y)

Q = plt.quiver( U, V, headlength=0, headaxislength=0)

###

produces exactly what we want, but generates some warnings:

/usr/local/lib/python2.7/dist-packages/matplotlib/quiver.py:622:

RuntimeWarning: divide by zero encountered in divide

shrink = length/minsh

/usr/local/lib/python2.7/dist-packages/matplotlib/quiver.py:623:

RuntimeWarning: invalid value encountered in multiply

X0 = shrink * X0[np.newaxis,:]

/usr/local/lib/python2.7/dist-packages/matplotlib/quiver.py:624:

RuntimeWarning: invalid value encountered in multiply

Y0 = shrink * Y0[np.newaxis,:]

We can get around this by using some tiny headlength (minsh =

self.minshaft * self.headlength) but it seems more natural to avoid

drawing one entirely. Would there be any objections to a pull request

which special-cased 0 to avoid this?

Doug

Hi! Bumping this upstream from Sage, where we use quiver to draw

slope fields. The following code

###

import matplotlib.pyplot as plt

import numpy as np

fig = plt.figure()

r = np.arange(10)

X,Y = np.meshgrid(r,r)

U, V = np.cos(X), np.sin(Y)

Q = plt.quiver( U, V, headlength=0, headaxislength=0)

###

produces exactly what we want, but generates some warnings:

/usr/local/lib/python2.7/dist-packages/matplotlib/quiver.py:622:

RuntimeWarning: divide by zero encountered in divide

shrink = length/minsh

/usr/local/lib/python2.7/dist-packages/matplotlib/quiver.py:623:

RuntimeWarning: invalid value encountered in multiply

X0 = shrink * X0[np.newaxis,:]

/usr/local/lib/python2.7/dist-packages/matplotlib/quiver.py:624:

RuntimeWarning: invalid value encountered in multiply

Y0 = shrink * Y0[np.newaxis,:]

We can get around this by using some tiny headlength (minsh =

self.minshaft * self.headlength) but it seems more natural to avoid

drawing one entirely. Would there be any objections to a pull request

which special-cased 0 to avoid this?

No objections at all; it sounds like a good idea.

Eric

## ···

On 03/11/2012 12:27 PM, D. S. McNeil wrote:

Doug

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