sprogg sprogg - 6 months ago 57
Python Question

Value error x and y must be same size, but they are?

I'm trying to plot to numpy arrays both of length 10 against one another:

mass_frac_plot = plt.figure()
mass_frac = mass_frac_plot.add_subplot(1, 1, 1)
mass_frac.scatter(mass_frac, homogen_frac)


I get this:

Traceback (most recent call last):
File "./plot.py", line 58, in <module>
mass_frac.scatter(mass_frac, homogen_frac)
File "/usr/local/lib/python3.5/site-packages/matplotlib/__init__.py", line 1811, in inner
return func(ax, *args, **kwargs)
File "/usr/local/lib/python3.5/site-packages/matplotlib/axes/_axes.py", line 3836, in scatter
raise ValueError("x and y must be the same size")


Help! They really are both arrays and of length 10...

print(type(mass_frac), len(mass_frac))
print(mass_frac)
print(type(homogen_frac), len(homogen_frac))
print(homogen_frac)


Gives this:

<class 'numpy.ndarray'> 10
[ 3.67 3.6 4.45 3.74 4.93 4.35 3.89 5.62 4.73 3.83]
<class 'numpy.ndarray'> 10
[ 98.02982123 96.82921968 88.8207858 83.37174016 75.55236146
87.71156752 91.95410515 66.34245085 77.63112123 119.74640558]

DSM DSM
Answer

Help! They really are both arrays and of length 10...

No, they're not:

mass_frac_plot = plt.figure()
mass_frac = mass_frac_plot.add_subplot(1, 1, 1)
^^^^^^^^^
mass_frac.scatter(mass_frac, homogen_frac)
                  ^^^^^^^^^

After you execute your second line, mass_frac is clearly no longer an array at all. Instead, it'll be of type

>>> type(mass_frac)
<class 'matplotlib.axes._subplots.AxesSubplot'>

Change the variable name so you're not clobbering your array.

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