This help entry describes a number of features that are available for manipulating displayed graphs. These features are not available in any of the utilities from the Utilities menu. They can be used only when the active window is a function display window that is showing a graph. (A function window is opened when you create a new function or when you double-click on a function name in the Function List window. You can change the type of display in the active window to a graph by using the "As Graph" command from the Display menu.)
When you move the mouse cursor over a graph display, it will change from the usual arrow cursor to a "knife." This knife can be used to "cut out" a rectangular section of the display to be magnified. Press the mouse button at one corner of the rectangle you want to enlarge, and then move the mouse to the opposite corner. A frame is drawn around the selected rectangle. When you release the mouse button, the old graph will be erased, and an enlarged image of the selected rectangle will be displayed instead. You can repeat this process to obtain further enlargements.
If you hold down the command key while the cursor is over a graph display, you will see a "cross" cursor instead of the knife. If you click the mouse button while holding down the command key, the x-value of the current cursor location will be entered into the "Input" box of the window, and the output box and graph display will be updated accordingly. This provides an alternative to typing in the input value.
There are three commands in the Display menu that apply to graph displays, "Equalize Scales on Axes", "Fit Y-Axis to Graph", and "Restore Limits on Axes". The first two are available whenever a graph is displayed in the front window; they are used to adjust the range of x and/or y values used on the axes in the display.
"Equalize Scales on Axes" will expand the range of either x or y values so that a unit interval will have the same length on both axes. This will allow you, for example, to estimate slope visually.
"Fit Y-Axis to Graph" will adjust the range of values on the y-axis so that the minimum and maximum y-values displayed are the minimum and maximum y-values for the function, on the range of x-values displayed on the x-axis. (If the function has an asymptote in that range, xFunctions will try to do something reasonable).
The third command, "Restore Limits on Axes", is available only when you have modified a graph display with the "Equalize Scales on Axes" or "Fit Y-Axis to Graph" commands, or by using the knife cursor to enlarge a part of the display. This command will restore the minimum and maximum values on the x and y axes to their default values, the values they had when the window was first opened. The new limit values will also be lost if you close the window, modify the function, or change the display to table, expression, or diagram style.
