set1limtight

set ylim tight for the current xlim range of a plot (xlim stays unchanged); incl. option for xlim

After setting xlim (or zooming), it is sometimes useful to set ylim to the full range of the ydata WITHIN xlim.
ylim([-inf inf]) will set ylim at min(ydata) to max(ydata)."axis tight" does the same, and also sets xlim([min(xdata) max(xdata)]). In both cases ylim is calculated from the full ydata, and not just the ydata that is visible at the current xlim.

set1limtight('y') sets ylim to min and max of the ydata within range xlim. It leaves xlim unchanged.
set1limtight('x') same for xlim
set1limtight('y',ah) sets ylim for axes handle ah

Example:
x = 0:0.1:7; y = [sin(x); sin(x+0.2)*0.95];
plot(x,y,'o-');
xlim([1.15 2.45]);
set1limtight('y')