View|Zoom In and View|Zoom Out menu
items or the corresponding toolbar buttons. Zoom In doubles the
zoom level (i.e. you can see half as much of the graph) and Zoom
Out halves the zoom level (i.e. you can see twice as much of the
graph).
Remember that you can also zoom in on a graph by dragging out a
rectangle with the Zoom mouse button (by default the right button). When you do
this, the view-port changes to show the region which you dragged out.
Centering the view
The View|Center
View menu item or toolbar button pans the view-port so that the origin
(where the x any y axes meet) is in the center of the graph window. This
command is often useful after zooming in on a rectangle as described above.