For example, let’s open files p6_1.Master.Scope - p6_9.Master.Scope from directory <Spectrum installation directory>\samples\oo. These are spectrum data acquired by spectrum analyzer Ocean Optics.
Files contain a lot of values corresponding to whole wavelength range the device can measure. Obviously the most of these values absolutely have no meaning for us. Let’s suppose we do not want care about what exact range signal is suited in.
In this case we just can frame interested area by mouse to fit it into screen. Select all the graphs (Ctrl+A) and remove redundant points (Shift+Ctrl+T). Turn plot axes into automatic limits mode (Alt+=) and watch the result: | 
