Sizing Data by Expression :: Defining Events and Data (Stateflow User's Guide)

Stateflow User's Guide

Sizing Data by Expression

You set the Size property for an array in [row column page] format. For example, a value of [2 4] defines a 2-by-4 matrix in [row column] format. To define a row vector of size 5, set the Size to [1 5]. To define a column vector of size 6, set the Size property to [6 1] or just 6.

You can enter a MATLAB expression for each element (row, column, page) in the Size field that uses one or more of the following:

Numeric constants -- For example, 1, 3, 7.54, and so on.
Arithmetic operators -- Restricted to +, -, *, and /.
Stateflow constants -- Read-only variables for Stateflow declared in the Model Explorer with a scope of Constant. They retain the value they are initialized with, which is set in the Data dialog or Contents pane of the Model Explorer. See Setting Value Attribute Data Properties for details on setting the initial value in the Data dialog.
Parameters -- Read-only data for the Stateflow chart declared in the Model Explorer with the scope Parameter. They take their value from a Simulink parameter of the same name for a parent masked subsystem or from a variable in the MATLAB base workspace. See Initializing Data from the MATLAB Base Workspace for more information on data with the scope Parameter in Stateflow.
Calls to the MATLAB functions min, max, and size.

Note The result of the expression you enter for the size of data must resolve to a positive integer, or an error results. For example, the expression x+y, where x=4.21 and y=3.79, results in a size of 8.00, which is acceptable. However, if x=4.22 instead, this results in a size of 8.01, which flags an error.

By using parameterized sizing, you can quickly resize large numbers of data by changing the size of a single Simulink parameter or MATLAB variable. If k, x, and y are Stateflow data of scope Constant or Parameter, the following examples are valid expressions that you can enter in the Size field of other data:

```
k+1
size(x)
min(size(y),k)
```

Note You cannot size Stateflow input data with an expression that accepts frame-based data from Simulink.

Once you build the model, the CompiledSize column of the Model Explorer gives the actual size used in the compiled simulation application. In the following example, the Stateflow block input variable uin is sized by the expression x+y.

x is a local data with the scope Parameter that takes its value from the parameter x for the masked subsystem containing the Stateflow block. Its value is initialized to 2.1. y is a local variable of scope Constant initialized to 3.9. x+y is therefore 6.

Inheriting Input and Output Data Size from Simulink Using Actions in Stateflow