title: Numpy isfinite typeerror
body: <p>I know I'm doing it wrong but I don't see how to do it right. In my executing code, the series I have comes from a large dataframe that I've done a groupby on. In the real code, the assignment happens in a loop as select various slices from the series.</p>
  
  <p>The code below results in TypeError: ufunc 'isfinite' not supported for the input type. I'm positive that this is due to a reference, not a copy or something on that line, but I'm just not good enough in Python to understand how to fix it.</p>
  
  <pre><code>import sys
  import numpy as np
  import pandas as pd
  import random
  import matplotlib.pyplot as plt
  
  plt.ion()
  period = 36
  ward_dates = pd.date_range(start=pd.datetime.today(), freq='M', periods=period)
  list_size = 6
  ward_counts = [[] for i in range(list_size)]
  for idx in range(list_size):
      current_list = [np.random.randint(0, 500000) for r in range(period)]
      ward_counts[idx] = current_list
  plt.stackplot(ward_dates, ward_counts)
  plt.close('all')
  
  units = np.random.choice(['U1', 'U2', 'U3'], size=period)
  index = pd.MultiIndex.from_arrays([units, ward_dates])
  s1 = pd.Series([np.random.randint(0, 5000) for r in range(period)], index=index)
  
  ward_counts = [[] for i in range(3)]
  l1 = [int(x) for x in s1.loc['U1'].values]
  ward_counts[0] = l1
  l1 = [int(x) for x in s1.loc['U2'].values]
  ward_counts[1] = l1
  l1 = [int(x) for x in s1.loc['U3'].values]
  ward_counts[2] = l1
  plt.stackplot(ward_dates, ward_counts)
  </code></pre>
  
  <p>The first stackplot works just fine. The second fails. I know therefore the issue is in grabbing the values. The resulting lists both LOOK identical (ints with the same number of values) but the second fails.</p>
  
  <p>I've looked at slicing, deepcopy, etc. but they continue to fail, so the fundamental problem is my lack of understanding. I'm also sure this is a duplicate of many others but i just don't grasp the issue. </p>
  
  <p><strong>Update</strong></p>
  
  <p>Here is the trackback</p>
  
  <blockquote>
    <p>File
    "C:/Users/dgrawroc/PycharmProjects/fs_admin_reports/fs_admin_reports/oldstuff.py",
    line 47, in main
        plt.stackplot(ward_dates, ward_counts)   File "C:\Users\dgrawroc\Documents\Anaconda3\envs\m2\lib\site-packages\matplotlib\pyplot.py",
    line 3326, in stackplot
        ret = ax.stackplot(x, *args, **kwargs)   File "C:\Users\dgrawroc\Documents\Anaconda3\envs\m2\lib\site-packages\matplotlib__init__.py",
    line 1811, in inner
        return func(ax, *args, **kwargs)   File "C:\Users\dgrawroc\Documents\Anaconda3\envs\m2\lib\site-packages\matplotlib\axes_axes.py",
    line 4443, in stackplot
        return mstack.stackplot(self, x, *args, **kwargs)   File "C:\Users\dgrawroc\Documents\Anaconda3\envs\m2\lib\site-packages\matplotlib\stackplot.py",
    line 113, in stackplot
        **kwargs))   File "C:\Users\dgrawroc\Documents\Anaconda3\envs\m2\lib\site-packages\matplotlib__init__.py",
    line 1811, in inner
        return func(ax, *args, **kwargs)   File "C:\Users\dgrawroc\Documents\Anaconda3\envs\m2\lib\site-packages\matplotlib\axes_axes.py",
    line 4608, in fill_between
        y2 = ma.masked_invalid(self.convert_yunits(y2))   File "C:\Users\dgrawroc\Documents\Anaconda3\envs\m2\lib\site-packages\numpy\ma\core.py",
    line 2293, in masked_invalid
        condition = ~(np.isfinite(a)) TypeError: ufunc 'isfinite' not supported for the input types, and the inputs could not be safely
    coerced to any supported types according to the casting rule ''safe''</p>
  </blockquote>