Maps chart axes to points, relative to the current frame.This is useful for positioning text output and drawing arbitrary polylines with chDraw e.g. to annotate data points or write your own text on Gantt charts.

It may also be used to offset notes by a fixed amount from a datapoint, for example:

chNote(›'Point 4;with offset'),4 ¯3 + chMapCoords mat[4;]

This will write the text 4 points to the right of the data and drop the baseline by 3 points. The sample function Annotations shows some possibilities here.