Re: [Matplotlib-users] ValueError: x and y must have same first dimension

[Daπid <dav...@gm...>]

In the example you provide, bins is returned by the hist command,
whereas in your code, bins is a number that you defined as 20. So,
change:

bins = 20
plt.hist(C, bins, ...

by:

nbins = 20
n, bins, patches = plt.hist(C, nbins, ...


As a side comment, your data loading is too complex, and fail prone. I
suggest you to have a look at the numpy function for that, loadfromtxt
or (I like it more), genfromtxt. It would be something like:

data=np.genfromtxt(F, delimiter=' ')
C=data[:,3]

Much easier, and way faster.


Regards,

David.

On Fri, Jul 27, 2012 at 4:13 AM, surfcast23 <sur...@gm...> wrote:
>
> Hi
> I have a code to plot a histogram and I am trying to add a best fit line
> following this example
>
> http://matplotlib.sourceforge.net/examples/pylab_examples/histogram_demo.html
>
> but run into this error
>
> Traceback (most recent call last):
>   File "/home/Astro/count_Histogram.py", line 54, in <module>
>     l = plt.plot(bins, y, 'r--', linewidth=1)
>   File "/usr/lib/pymodules/python2.7/matplotlib/pyplot.py", line 2467, in
> plot
>     ret = ax.plot(*args, **kwargs)
>   File "/usr/lib/pymodules/python2.7/matplotlib/axes.py", line 3893, in plot
>     for line in self._get_lines(*args, **kwargs):
>   File "/usr/lib/pymodules/python2.7/matplotlib/axes.py", line 322, in
> _grab_next_args
>     for seg in self._plot_args(remaining, kwargs):
>   File "/usr/lib/pymodules/python2.7/matplotlib/axes.py", line 300, in
> _plot_args
>     x, y = self._xy_from_xy(x, y)
>   File "/usr/lib/pymodules/python2.7/matplotlib/axes.py", line 240, in
> _xy_from_xy
>     raise ValueError("x and y must have same first dimension")
> ValueError: x and y must have same first dimension
>
> My Code
>
> import matplotlib.pyplot as plt
> import math
> import numpy as np
> import mpl_toolkits.mplot3d.axes3d
> import matplotlib.mlab as mlab
>
> counts = []
> F = '/home/Astro/outfiles/outmag21_5dr_38_68.txt'
> f = open(F)
> for line in f:
>  if line != ' ':
>     columns = line.split()
>     count = columns[3]
>     count = int(count)
>     counts.append(count)
>     C  = np.array(counts, dtype=float)
>
> avg = sum(C)/len(C)
> diff = C-avg
> sigma = np.sqrt((1./len(C))*(diff**2))
>
> bins = 20
> plt.hist(C, bins, range=None, normed=False, weights=None, cumulative=False,
> bottom=None, histtype='bar', align='mid', orientation='vertical',
> rwidth=None, log = False, color=None, label=None)
> plt.title("")
> plt.text(25,20,'M < -21.5' '\n' 'N Halos 3877' '\n' 'Length Cell 38.68Mpc'
> '\n' 'N Cells 269' '\n' 'Avg Halo per Cell 14.35 ')
> plt.xlabel("Halos/Cell")
> plt.ylabel("Number Cells with N Halos")
> y = mlab.normpdf( bins, avg, sigma)
> print(len(y))
> l = plt.plot(bins, y, 'r--', linewidth=1)
> plt.show()
>
>
> My first question is do x and y refer to the values in  l = plt.plot(bins,
> y, 'r--', linewidth=1) which for my case are bins and y?
> if that is the case how can I get then to be the same first dimension?
> --
> View this message in context: http://old.nabble.com/ValueError%3A-x-and-y-must-have-same-first-dimension-tp34218704p34218704.html
> Sent from the matplotlib - users mailing list archive at Nabble.com.
>
>
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