This page explains how to change the tick labels:
Note that the solution depends on what MATLAB version you are using:
% For R2014b and later:
ax = gca;
ax.XTick = [-3*pi -2*pi -pi 0 pi 2*pi 3*pi];
ax.YTick = [-1 -0.5 0 0.5 1];
% For R2014a and earlier:
ax = gca;
set(ax,'XTick',[-3*pi -2*pi -pi 0 pi 2*pi 3*pi])
set(ax,'YTick',[-1 -0.5 0 0.5 1])
Note that you can also supply the labels as strings in a cell array, which is useful if you want to precisely control their format, how they are displayed, or non-numeric tick labels.
