方法一：

set(gca, 'XTick',[-3*pi -2*pi -pi 0 pi 2*pi 3*pi], 'XTickLabel', {'-3\pi','-2\pi','-\pi','0','\pi','2\pi','3\pi'});

方法二：

ax = gca;
ax.XTickLabel={'-8\pi','-2\pi','-\pi','0','\pi','2\pi','3\pi'};

For releases prior to R2016b, set the tick values and labels using the XTick, XTickLabel, YTick, and YTickLabel properties of the axes object. For example, assign the axes object to a variable, such as ax = gca. Then set the XTick property using dot notation, such as ax.XTick = [-3*pi -2*pi -pi 0 pi 2*pi 3*pi]. For releases prior to R2014b, use the set function to set the property instead.