Vision V350 has a good trend display library but I could not find a ready to use library to plot XY graphs where X does not means the time axis.
Sometimes you might need to relate two values like temperature X pressure in a graph form in order to make a better process analysis for instance and proposed solution shows a method to create a cursor and move that cursor in a plot area in accord two distinct values like shown below:
These two links below are about how to control the fan cooler PWM signal using a PLC (theory and practice) and the second one approaches the graphic design