title: Python Plot- Multiple the data in plot figure
body: <p>I am reading data from a text file but when I do so, I need to multiple this values like <code>3*sqrt(col1)</code>= <code>x1.append(3*math.sqrt(float(p[1])))</code>  in plot function. How can I multiple column number data before plotting? For example, I will multiple col3 data by 3*sqrt(col3) and after plot that data.</p>
  
  <pre><code>#-------input.dat---------
  #   x        y     z
  # col 1    col 2  col 3
  # 3          5      5
  # 5          6      4
  # 7          7      3
  import matplotlib.pyplot as plt
  import numpy as np
  import pylab as pl
  import math
  
  data = open('input.dat')
  lines = data.readlines()
  data.close()
  x1=[]
  y1=[]
  z1=[]
  plt.plot(1)
  for line in lines[2:]:
  p= line.split()
  x1.append(3*math.sqrt(float(p[1])))
  y1.append(3*math.sqrt(float(p[2])))
  z1.append(3*math.sqrt(float(p[3])))
  x=np.array(x1)
  y=np.array(y1)
  z=np.array(z1)
  plt.subplot(311)
  plt.plot(x,'b',label=" X figure ")
  plt.subplot(312)
  plt.plot(y,'r',label=" Y figure ")
  plt.subplot(313)
  plt.plot(x,z,'g',label=" X,Z figure ")
  plt.show()
  </code></pre>