Determination of visual interpolation errors in the plotting of curves from commutated data

The problem of data interpolation is one with which most engineers are quite familiar. Many results, obtained from experiments, are presented in the form of graphs, in which a number of measured points have been plotted and a curve has then been drawn through these points to represent the behaviour of the variable between the measured points. In general, such interpolation of data is done by a human being who, either free-hand, or with the help of French curves tries to produce a “smooth” curve which encompasses all the measured points.