COORD2NORM(axishandle, x, y) takes input XY coordinates, relative to the axes object axishandle, and normalizes them to the parent container of axishandle. This is useful for functions like annotation, where the input XY coordinates are normalized to the parent container of the plotting axes object and not to the data being plotted. axishandle must be a valid MATLAB axes object (HG2) or handle (HG1).
COORD2NORM returns discrete arrays xnorm and ynorm of the same size as the input XY coordinate arrays.
Example:

myaxes = axes();
x = -10:10;
y = x.^2;
plot(x, y);

[normx, normy] = coord2norm(myaxes, [x(1) x(2)], [y(1) y(2)]);
annotation('arrow', normx, normy);

Also included is the helper function NORM2COORD which performs the reverse operation, mapping coordinates normalized to the parent container of axishandle to the data space of axishandle.

This function builds on existing FEX submissions with the inclusion of logarithmic plot support (loglog, semilogx, semilogy).