Jeweler's Loupe

JEWELERSLOUPE modifies a figure to enable a Jeweler's Loupe tool.
JEWELERSLOUPE(FIG) will modify the figure with handle FIG to allow a
jeweler's loupe tool, which magnifies the axes by a factor of 4, to
appear whenever a user clicks on an axes. Dragging will cause the loupe
to follow the cursor. The tool assumes that any axes clicked will be a
linear 2-D axes. Performance will degrade as the amount of data in the
axes increates. If no figure is given, the loupe will appear in the
current figure.
Example:
plot(magic(3));
jewelersLoupe(gcf);