Actions

## Introduction

Actions provide a way to react to events in the calculator, like clicks or clock ticks. An action is composed of one or more update rules that each specify a new value for a variable, depending on a specific event within the expression list or the graph paper.
Use the resources below to enable Actions on your account and learn about all of the features that are available once they're enabled.

## Enabling Actions

You can enable actions at the account level to unlock the "clickable" feature and the ticker feature. However, you can use actions without changing your settings.

## Getting Started With Actions

Use a right arrow to author an action. You can write the → symbol by typing the subtraction symbol (-) followed by a greater than sign (>).

When you write an action in the expression list, make sure you enable the slider for the included variable.
The expression with the action will then display an action icon that will run the action every time you click on it.

Some examples of basic actions:
Set a to 1: a → 1
Increment a: a → a + 1
Swap the values of a and b: a → b, b → a

## Clickable Objects

When actions are enabled, you can attach an action to graphed objects like points, curves, and images. The action will run when the object is clicked in the graphing calculator window.

Long press the expression icon to bring up the style menu.

Toggle Clickable to the “on” position.

In the field titled On Click, you can author an action that will be performed when the object is clicked within the graphing calculator itself.

## The Ticker

When actions are enabled, you can specify an action that will run repeatedly at a specified interval.

To add a ticker, click the Add Expression button in the top left of the expression panel of the graphing calculator. You can also type ticker into an expression line.

Specify an action to run.
Optionally, specify how much time (in ms) should pass between ticks.

Click the icon next to the ticker to run the action repeatedly over the time interval.

## Actions using Variables and Function Notation

Actions can be assigned to variables:
A=a → 1
This allows attaching the same action to several objects.

Functions can also produce actions:
f(x)=a → x
This allows making related actions, so with this definition, f(1) and f(2) will be two different actions that set a to different values when they run.

Piecewise expressions (using restriction notation in curly braces) allow selecting between different actions depending on a condition.
You can do things like decrement a, but only if it is positive. Or, if a is not positive, set b to 1, otherwise, set c to 1.

## Pro Tips

When a click action is attached to a list, the special variable “index” represents which element of the list was clicked.
Click here to see an example of using Lists with actions.

In tick actions, the special variable dt represents how much time has passed since the last tick. You can use dt to track how long the ticker has been playing.
Click here to see an example graph that uses dt to measure the ticker time.

When random( ) is used in an action definition, a new random number will be used every time the action runs.
Click here to see random numbers used in an action.