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Purpose of Continuous-Time Variables Rules for Using Continuous-Time Variables |

To compute a continuous state, you must determine its rate of
change, or derivative. You can represent this information using *local* variables
that update in continuous time. In a Stateflow^{®} chart, continuous-time
variables are always `double` type. You cannot change
the type, but you can change the size.

For each continuous variable you define, a Stateflow chart
implicitly creates a variable to represent its time derivative. A
chart denotes time derivative variables as *variable_name*`_dot`.
For example, the time derivative of continuous variable `x` is `x_dot`.
You can write to the time derivative variable in the `during` action
of a state. The time derivative variable does not appear in the Model
Explorer.

Follow these rules when defining and using continuous-time variables:

Scope can be

`Local`or`Output`.Define continuous-time variables at the chart level or below in the Stateflow hierarchy.

Expose continuous state by assigning the local variable to a Stateflow output (see Expose Continuous States to a Simulink Model).

To define continuous-time variables, follow these steps:

Configure your chart to update in continuous time, as described in Configure a Stateflow Chart to Update in Continuous Time.

Add local data to your chart in the Stateflow Editor or Model Explorer.

In the properties dialog box for your local data, set

**Update Method**to`Continuous`.In this example, the chart automatically creates the variable

`mydata_dot`to represent the time derivative of this data.

In a Stateflow chart, you represent continuous state using
local variables, not inputs or outputs (see Purpose of Continuous-Time Variables). To expose the continuous
states to a Simulink model, you must explicitly assign the local
variables to Stateflow outputs in the `during` action
of the state. For examples, see Model a Bouncing Ball in Continuous Time.

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