title: Using Matplotlib, visualize CSV data
body: <p><a href="https://stackoverflow.com/questions/31245043/using-matplotlib-i-cannot-visualize-data-as-values-per-30mins-and-per-days">Using matplotlib/pandas/python, I cannot visualize data as values per 30mins and per days</a> is a new question, which is strongly related to this question.</p>
  
  <p>I want to visualize CSV data with Matplotlib.</p>
  
  <p>Following is my code named <code>1.30mins.py</code></p>
  
  <pre><code>import matplotlib.pyplot as plt
  from matplotlib import style
  import numpy as np
  
  style.use('ggplot')
  
  x,y =np.loadtxt('total_watt.csv',
                  unpack = True,
                  delimiter = ',')
  
  plt.plot(x,y)
  
  plt.title('Example')
  plt.ylabel('Y axis')
  plt.xlabel('X axis')
  
  plt.show()
  </code></pre>
  
  <p>When I implemtented <code>1.30mins.py</code>, I got a following error message.</p>
  
  <pre><code>(DataVizProj)Soma-Suzuki:Soma Suzuki$ python 1.30mins.py
  Traceback (most recent call last):
    File "1.30mins.py", line 10, in &lt;module&gt;
      delimiter = ',')
    File "/Users/Suzuki/Envs/DataVizProj/lib/python2.7/site-packages/numpy/lib/npyio.py", line 856, in loadtxt
      items = [conv(val) for (conv, val) in zip(converters, vals)]
  ValueError: invalid literal for float(): 2011-04-18 13:22:00
  </code></pre>
  
  <p>This is my <code>total_watt.csv</code></p>
  
  <pre><code>2011-04-18 21:22:00 659.670303375527
  2011-04-18 21:52:00 576.304871428571
  2011-04-18 22:22:00 2,497.20620579196
  2011-04-18 22:52:00 2,790.20392088608
  2011-04-18 23:22:00 1,092.20906629318
  2011-04-18 23:52:00 825.994417375886
  2011-04-19 00:22:00 2,397.16672089666
  2011-04-19 00:52:00 1,411.66659265233
  </code></pre>
  
  <p>As far as I searched by myself, I need to add <code>converters</code> or, <code>%y-%m-%t</code>　to my program.</p>
  
  <p>My python version is 2.76
  My matpltlib version is 1.42</p>