How To Construct a Slider

How to . . . Construct a Slider

Often it is useful to construct a slider for controlling a numeric value. For example, if you wanted to create a graph of the line y = mx + b in which you can slide a point back and forth to control the values of m and b, you might want to set up sliders for m and b. To make a slider for m:

1. Construct a line through two points A and B.

2. Use the Point tool to construct a point C on the line.

3. Select A, B, and C in that order, and choose Ratio from the Measure menu.

4. Select and hide the line and point B, leaving only two points and the measured ratio.

5. Construct a segment connecting A and C.

6. Double-click the measured ratio with the Text tool, and set its label to m.

Your basic slider is complete. As you drag C, the value of m changes accordingly. If you want, you can improve on the slider by hiding A, by hiding the label of C or changing C’s label to something more meaningful, or by using Calculate to multiply m by a constant, creating a new value that spans a larger (or smaller) range than the original value of m as you drag C.

You can also create a numeric value directly, using the New Parameter command from the Graph menu. The advantage of the slider described here is that sliding the control point back and forth provides a powerful, visual way to change the value.