# Parameters

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Parameters are simple numeric values. Unlike measurements and calculations, they do not depend on other objects for their value. A parameter is defined by a single number and an optional unit. Use parameters to define mathematical constructions when you want to explore the effects on the construction of varying a numeric quantity. |

There are three kinds of parameters:

• | Angle parameters have units of degrees or radians.

• | Distance parameters have units of pixels, cm, or inches.

A pixel is one dot on the screen, and is the smallest distance you can move the pointer.

• | Dimensionless parameters have no units.

Once a parameter is defined, you can easily change its value by typing new values or by animating the parameter so that it changes value gradually over some numeric domain.

A parameter can display an edit box. Such a parameter is called a boxed parameter, and can be edited directly in the sketch. (Use the parameter's Value Properties to determine whether it has an edit box.)

Parameters and Sliders

To create an easily modified numeric value, use either a parameter or a slider. A parameter is easier to create, and you can adjust it more precisely and easily animate it over a specific numeric range. A slider is harder to create, but you can manipulate it easily (by dragging the point at the tip) and control it in a continuous and satisfying way.

| Create a Parameter

• | Choose Number | New Parameter (or press Shift+Ctrl+P on Windows or Shift-P on Mac), or
• | Choose New Parameter from the Calculator’s Value pop-up menu (or press Shift+Ctrl+P on Windows or Shift-P on Mac).
In the New Parameter dialog box that appears, type an initial value for the parameter and determine the units of the parameter. Note
The initial value you type determines both the value and the keyboard adjustment used when you press the + or – key. The keyboard adjustment is based on the least significant digit that you type for the value. For instance, if you type 5, the keyboard adjustment will be 1. If you type 5.0, the keyboard adjustment will be 0.1. And if you type 5.00, the keyboard adjustment will be 0.01. To change the keyboard adjustment later, choose Edit | Properties | Parameter.

| Change the Value of a Selected Parameter

Use the parameter's Value Properties to determine whether it has an edit box allowing its value to be edited directly in the sketch.
• | Directly edit the value of a parameter that has an edit box. Click the Arrow or Text tool in the edit box to begin editing, or select the parameter and press Return or Tab. To finish editing, click outside the edit box or press Esc.
• | Press TAB while editing a parameter's edit box to advance to the next editable parameter value.
• | Double-click the parameter with the Arrow tool to use a dialog box to change the value or the label. (If the parameter has an edit box, you must double-click outside the edit box.)
• | Drag-adjust the parameter as described below.
• | Choose Edit | Properties and type a new number in the Value panel.
• | Select the parameter and press the + or – key on your keyboard.
• | Choose Increase Value or Decrease Value from the Context menu.
• | Create a Movement button to change the parameter to a particular value.

| Drag-Adjust a Boxed Parameter

Press inside the edit box and drag or flick up or down to adjust a boxed parameter's value. The parameter changes by the Keyboard Adjustment value, and continues to change as long as you press. For faster adjustments, drag farther up or down; for slower adjustments, drag closer to the edit box you are adjusting. (You can use this method whether the parameter is selected or not, provided you have not already begun to edit the number in the edit box.)

| Animate a Parameter

• | Select it and choose Display | Animate, or
• | Select it and click the Motion Controller’s Animate button, or
• | Use an Animation action button. Select the parameter and choose Edit | Action Buttons | Animation.

| Modify a Parameter’s Default Domain, Speed, or Other Properties

To determine how the parameter is animated and how its value changes when you press the + or – key, select the parameter and choose Edit | Properties | Parameter.

| Change a Parameter into a Calculation

Select the parameter, choose Edit | Edit Parameter, and use the Calculator to redefine the parameter as a calculation based on other values.