The center of the X axis in the graph, shown by the red vertical line, is maintained at the current image point (when graphing along an axis), at the current model point (when graphing along a contour), or at the intensity of the current image point (for a histogram). This is not quite the case when using the rubber band with a graph along a contour where the current point is outside the rubber band. Here, the center point of the display is kept near the edge of the rubber band, but the current model point is not changed to match.
When data are read in from a byte file, scaling the values may result in a histogram with many empty bins interspersed with bins full of counts. To avoid this effect, read the data in without scaling, i.e., with minimum and maximum scaling values set to 0 and 255 (-s 0,255).