title: plotting a histogram for a column in a csv file in python
body: <p>I am trying to plot a histogram and a scatter plot for a particular column in a given csv file. I am new to programming and I got this code from a friend, and it apparently works but somehow I am getting this error. the code is:</p>
  
  <pre><code>import csv
  import numpy as np
  import matplotlib.pyplot as plt
  f = open('Data for question 13.csv')
  data = csv.reader(f)
  Area = []; MajorAxisLength = []; MinorAxisLength = []; Perimeter = []
  MinIntensity = []; MeanIntensity = []; MaxIntensity = []
  header = [Area, MajorAxisLength, MinorAxisLength,Perimeter,MinIntensity,MeanIntensity,MaxIntensity]
  for row in data:
      i = 1 
      for name in header:
          name.append(row[i])
          i = i + 1
  plt.figure()
  plt.hist(Area, bins=50) # error follows after this
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;pyshell#11&gt;", line 1, in &lt;module&gt;
      plt.hist(Area, bins=50, alpha=0.5)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/pyplot.py", line 2827, in hist
      stacked=stacked, **kwargs)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/axes.py", line 8312, in hist
      xmin = min(xmin, xi.min())
    File "/Library/Python/2.7/site-packages/numpy-1.9.0-py2.7-macosx-10.9-intel.egg/numpy/core/_methods.py", line 29, in _amin
      return umr_minimum(a, axis, None, out, keepdims)
  TypeError: cannot perform reduce with flexible type
  </code></pre>
  
  <p>I am unable to get rid of this error.
  The answer should be simple but since I am new I have no idea how to deal with it. </p>