This page details the file format when a graph (line or histogram) is written to disk. This is done, for example, from the Profile frame, or the ROI Histogram frame.
A graph file is a plain text file, consisting of two columns of numerical data, where the first column is the x-values for the graph, and the second is the y-values. The two columns are separated by white space consisting of a single TAB character.
For a Profile, the x-value is the horizontal or vertical position (in pixels or millimetres, depending on the setting of the units display), while for a Histogram it is the image intensity. For a Profile, the y-value is the image intensity, while for a Histogram it is the number of pixels in the histogram bin.