Regression in scatter plot?

Community matplotlib-users
1

Hi,

according to the documentation, scatter should accept a 1D float array for color kwarg. Therefore, I thought the following code would work (and I think it worked at some point in the past; I'm currently using matplotlib 0.99.0):

import numpy as N
from matplotlib import pyplot as P

x = N.random.randn(100)
y = N.random.randn(100)
z = N.random.randn(100)**2

fig = P.figure()
ax = fig.add_subplot(1,1,1)

cmap = P.matplotlib.cm.jet
norm = P.matplotlib.colors.Normalize(vmin=0, vmax=1)

sc = ax.scatter(x,y,
                 color=z,
                 cmap=cmap,
                 norm=norm,
                 )

But this crashes with the following error:

[...]
/data/ycopin/Softs/local/lib/python2.4/site-packages/matplotlib/colors.pyc in to_rgba_array(self, c, alpha)
     377 if isinstance(c, np.ndarray):
     378 if c.ndim != 2 and c.dtype.kind not in 'SU':
--> 379 raise ValueError("Color array must be two-dimensional")
     380 if (c.ndim == 2 and c.shape[1] == 4 and c.dtype.kind == 'f'):
     381 if (c.ravel() > 1).any() or (c.ravel() < 0).any():

ValueError: Color array must be two-dimensional

So my question is: is the documentation just outdated, or is it a regression in scatter?

Cheers,

···

--
    .~. Yannick COPIN (o:>* Doctus cum libro
    /V\ Institut de physique nucléaire de Lyon
   // \\ Université de Lyon - CNRS-IN2P3
  /( )\ AIM: YnCopin ICQ: 236931013
   ^`~'^ http://snovae.in2p3.fr/ycopin/

2

Hello,

According to http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.scatter , the keyword argument that takes an array to specify the colors of the individual markers is c. color is interpreted as a color to give to all markers at once.

The following works on my computer (matplotlib 0.99.0) :

import numpy as N
from matplotlib import pyplot as P

x = N.random.randn(100)
y = N.random.randn(100)
z = N.random.randn(100)**2

fig = P.figure()
ax = fig.add_subplot(1,1,1)

cmap = P.matplotlib.cm.jet
norm = P.matplotlib.colors.Normalize(vmin=0, vmax=1)

sc = ax.scatter(x,y,
                  c=z,
                  cmap=cmap,
                  norm=norm,
                  )

···

Le 10 déc. 09 à 14:44, Yannick Copin a écrit :

Hi,

according to the documentation, scatter should accept a 1D float array for
color kwarg. Therefore, I thought the following code would work (and I think
it worked at some point in the past; I'm currently using matplotlib 0.99.0):

import numpy as N
from matplotlib import pyplot as P

x = N.random.randn(100)
y = N.random.randn(100)
z = N.random.randn(100)**2

fig = P.figure()
ax = fig.add_subplot(1,1,1)

cmap = P.matplotlib.cm.jet
norm = P.matplotlib.colors.Normalize(vmin=0, vmax=1)

sc = ax.scatter(x,y,
                 color=z,
                 cmap=cmap,
                 norm=norm,
                 )

But this crashes with the following error:

[...]