title: matplotlib.pyplot errorbar ValueError depends on array length?
body: <p>Good afternoon.</p>
  
  <p>I've been struggling with this for a while now, and although I can find similiar problems online, nothing I found could really help me resolve it. </p>
  
  <p>Starting with a standard data file (.csv or .txt, I tried both) containing three columns (x, y and the error of y), I want to read in the data and generate a line plot including error bars.</p>
  
  <p>I can plot the x and y values without a problem, but if I want to add errorbars using the matplotlib.pyplot errorbar utility, I get the following error message:</p>
  
  <p><code>ValueError: yerr must be a scalar, the same dimensions as y, or 2xN.</code></p>
  
  <p>The code below works if I use some arbitrary arrays (numpy  or plain python), but not for data read from the file. I've tried converting the tuples which I obtain from my input code to numpy arrays using asarray, but to no avail. </p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  
  row = []
  with open("data.csv") as data:
      for line in data:
          row.append(line.split(','))
  
  column = zip(*row)
  
  x = column[0] 
  y = column[1]
  yer = column[2]
  
  plt.figure() 
  plt.errorbar(x,y,yerr = yer)
  
  fig = plt.gcf()
  fig.set_size_inches(18.5, 10.5)
  fig.savefig('example.png', dpi=300)
  </code></pre>
  
  <p>It must be that I am overlooking something. I would be very grateful for any thoughts on the matter.</p>