title: Converting relative time from CSV file into absolute time
body: <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  from scipy.interpolate import Rbf, InterpolatedUnivariateSpline
  data = np.genfromtxt('FTIR Data.csv',  skip_header=1, delimiter=',', usecols=(1,2,3), names=['Time','Peakat2188cm1', 'water']  ) 
  
  x=data['Time']
  y1=data['Peakat2188cm1']
  y2=data['water']
  
  fig=plt.figure()
  ax1 = fig.add_subplot(111)
  ax2 = ax1.twinx()
  
  ius=InterpolatedUnivariateSpline
  xs = np.linspace(x.min(), x.max(), 100)
  s1=ius(x,y1)
  s2=ius(x,y2)
  ys1 = s1(xs)
  ys2 = s2(xs)
  
  ax2.plot(xs,ys1) 
  ax2.plot(xs,ys2)
  ax1.set_ylabel('Peak at 2188 cm-1')
  ax2.set_ylabel('water')
  ax1.set_xlabel('RT (mins)')
  plt.title('RT Vs Conc')
  </code></pre>
  
  <p>This is my code for reading data from a csv file which is an export data from my instrument. In excel file, i have manually converted the relative time into Time in minutes and got the right plot. But i want to convert the relative time directly in matplotlib when reading the relative time column in csv file.  I have tried from different examples but couldnt get through. I am very new to python so can anyone please help  with editing in my code. My actual data is in the following format. (this code is used to plot absolute time i.e. Time, which i already converted in excel before ploting in matplotlib)[enter image description here][1]</p>
  
  <pre><code>Relative Time,Peak at 2188 cm-1,water
  00:00:51,0.572157,0.179023
  00:02:51,0.520037,0.171217
  00:04:51,0.551843,0.221285
  00:06:50,0.566279,0.209182
  00:09:26,0.022696,0.0161351
  00:10:51,-0.00344509,0.0141303
  00:12:51,0.555898,0.21082
  00:14:51,0.519753,0.179563
  00:16:51,0.503512,0.150133
  00:18:51,0.498554,0.154512
  00:20:51,0.00128343,-0.0129148
  00:22:51,0.349077,0.0414234
  00:24:50,0.360565,0.0522027
  00:26:51,0.403705,0.0667703
  </code></pre>
  
  <p>Plot </p>
  
  <p><img src="https://i.stack.imgur.com/jJ5YX.png" alt=""></p>