title: Plotting the difference between two parallel measurements on a different time base in MatPlotLib
body: <p>I have run an experiment where I am measuring the same parameter with two devices: One is under test, and the other is calibrated. They both generate a csv that I am importing into two separate dataframes in pandas of the form:</p>
  <p>TimeStamp,MeasurementValue</p>
  <p>The device under test and the calibrated measurement device have different sampling rates, so the measurement TimeStamps of the two csv files don't perfectly line up. There will also be multiple data points on the device under test for every data point on the calibrated measurement device.</p>
  <p>DF1 (EUT)
  TimeStamp,MeasurementValue</p>
  <p>1602531853.36496,400</p>
  <p>1602531853.56531,390</p>
  <p>DF2
  TimeStamp,MeasurementValue</p>
  <p>1602531853.40507,415</p>
  <p>1602531853.80492,405</p>
  <p>I would like to plot the difference between the two curves as efficiently as possible because there are tens of thousands of data points.</p>