Parallel coordinate plot with smooth lines?
Tue, 03/16/2021 - 09:09 am
I have always found Parallel coordinate plots (https://en.wikipedia.org/wiki/Parallel_coordinates) bit difficult to read and enough confusing not to use them. Recently I saw the same plot with smooth curves instead of straight lines and found it surprisingly better for human eye. See attached figure.
I would like to find way to generate these from my results in Igor. I am running into some issues creating the smooth curves connecting the data points. I tried playing with Interpolate2 cubic spline, but it is not resulting in what I need. It does not guarantee that derivative of the curve in each point (crossing each vertical line) is 0 so it generates curves which have maxima and minima away from the data points / lines. See maximum on spline curve in my plot around 2.3 and minimum around 3.8.
Wikipedia even has link to paper which discusses what needs to be satisfied to make these lines look as expected. Reference 7 on https://en.wikipedia.org/wiki/Parallel_coordinates
Anyone has suggestion how to generate these spline curves in Igor?