title: Extra lines in plot when using matplotlib.plot
body: <p>I'm trying to make a program that will create a descending series of plots based on given files containing an n*2 matrix of numerical values (they more or less share an x-axis, and they're close enough on the y-axis that they need to be manipulated to avoid overlap).</p>
  
  <p>Right now, the way it works is to read in the files one at a time with fileinput, add a constant to the values in column two (arbitrary so long as the constant splits each plot; I do it by multiplying the number of files by two, and decrementing by two each plot so they get split), then add the manipulated values to two master lists (for x and y), which are plotted at the end by matplotlib.</p>
  
  <p>I have it doing very close to exactly what I want, but it has some odd lines connecting the end of one file to the beginning of the next, and I'd like to know how to remove them.</p>
  
  <p>Here's the relevant part of the code:</p>
  
  <pre><code>mpl.suptitle(spectitle, fontsize=16)
  mpl.xlabel('wavelength (A)', fontsize=14)
  mpl.ylabel('flux (erg s^-1 cm^-2)', fontsize=14)
  
  with open(filelist) as infile:
      allfiles = [line.rstrip('\n') for line in open(filelist)]
  
  multiplier = len(allfiles)
  multiplier *= 2
  
  for line in fileinput.input(allfiles):
      filename = fileinput.filename()
      waveN, fluxN = np.loadtxt(filename, usecols=[0,1], unpack=True)
      fluxCalc = np.array(fluxN)
      fluxCalc += multiplier
      multiplier -= 2 #decrease multiplier, causing next output specturm to be placed below the one just calculated
      wavelenAll.extend(waveN)
      fluxCalc.tolist()
      fluxAll.extend(fluxCalc)
      fileinput.nextfile()
  
  mpl.plot(wavelenAll, fluxAll)
  mpl.savefig('allspec.png')
  mpl.show()
  </code></pre>
  
  <p>I can add an image of the output in a few hours. Thanks for any help in advance.</p>