Editing Control Points

Controls points are used to define the shape of the function. The following operations are possible when working with control points:

select: To select a control point, use ctrl+left mouse on the point. To select multiple points, use ctrl+shift+left mouse on the points. You can also "box select" points by holding down the ctrl+left mouse button and dragging the cursor to form the selection box. You can also hold down the shift key while box selecting to select multiple sets of control points. Selected control points are displayed in yellow.

add:  To add a control point to the function, put the cursor where you would like to add the point and press the right mouse button. Choose Add control point from the drop down menu that appears, and a new point will be added to the function.

delete: To delete a control point, put the cursor over the point and press the right mouse button. Choose Delete control point from the drop down menu.

duplicate point:  To duplicate a control point, put the cursor over the point you would like to duplicate, and press the right mouse button. Choose Duplicate control point from the drop down menu. A very small offset will be added to the point in the X direction, so that it is not exactly coincident with the chosen point. This is done because many types of functions require the control points to be monotonically increasing in the X direction.

move point:  Select one or more control points. Then, put the cursor over any of the selected points and press the left mouse button. While holding the button down, drag the set of points within the plot area. You cannot move the points over one of the adjacent points (i.e., the points in the X direction must always be monotonically increasing).

While you are dragging control points, crosshairs are displayed along with the XY coordinates of the control point under the cursor. Because the displayed coordinates are for the control point, not the actual location of the tip of the cursor, they can help you more accurately position the control point while dragging.

To more precisely move a control point, you can select it and then type its XY coordinates into the X and Y number fields below the plot area. When there are multiple points selected, you can type in a Y value to set all selected points to that value, but you cannot set the X value (because that would create coincident points).