matplotlib: TypeError: a float is required

[John Machin]

Andi Clemens wrote:
> Hi,
>
> everytime I try to plot a bar with matplotlib I get the following error
> message:
> Traceback (most recent call last):
>    File "bar_stacked.py", line 13, in ?
>      p1 = bar(ind, menMeans,   width, color='r', yerr=womenStd)
>    File "/usr/lib/python2.4/site-packages/matplotlib/pylab.py", line
> 1641, in bar
>      ret =  gca().bar(*args, **kwargs)
>    File "/usr/lib/python2.4/site-packages/matplotlib/axes.py", line
> 2485, in bar
>      xerr = asarray([xerr]*nbars, Float)
>    File "/usr/lib/python2.4/site-packages/Numeric/Numeric.py", line 134,
> in asarray
>      return multiarray.array(a, typecode, copy=0, savespace=savespace)
> TypeError: a float is required
>
>
> So I guess it has something to do with Numeric.py, but I can't figure
> out what the problem is. I tried to google but found nothing...
>
> Anyone has the same problem? I can plot all kinds of graphics with
> matplotlib, but the only type I'm interested in (bars) will not work.
>
> I tried the examples coming with matplotlib, but even those don't work.
>
> Here is the example code which produces the above error:
> #!/usr/bin/env python
> # a stacked bar plot with errorbars
> from pylab import *
>
> N = 5
> menMeans   = (20, 35, 30, 35, 27)
> womenMeans = (25, 32, 34, 20, 25)
> menStd     = (2, 3, 4, 1, 2)
> womenStd   = (3, 5, 2, 3, 3)
> ind = arange(N)    # the x locations for the groups
> width = 0.35       # the width of the bars: can also be len(x) sequence
>
> p1 = bar(ind, menMeans,   width, color='r', yerr=womenStd)

Call me crazy -- I know SFA about matplotlib -- but I'd expect anything
scientific to barf if given tuples of integers to play with, and
following the docs links matplotlib > pylab > bar we find:
"""
bar(*args, **kwargs)
    BAR(left, height, width=0.8, bottom=0,
        color='b', yerr=None, xerr=None, ecolor='k', capsize=3)
    Make a bar plot with rectangles at
      left, left+width, 0, height
    left and height are Numeric arrays.
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
"""

Which of us is missing what?

Cheers,
John