In a Stateflow® chart in a Simulink® model, you specify the size of a data object by:
Setting the Size property, as described in Set Data Properties. For more information, see Size.
Setting the Props.Array.Size property through the Stateflow API. For more information, see Stateflow.Data.
Use one of these methods to specify the size:
Inherit the size from a Simulink signal or from its definition in the Stateflow chart.
Enter a numeric value.
Enter a MATLAB® expression.
Support for each sizing method depends on the scope of your data.
| Scope of Data | Method for Sizing Data | ||
|---|---|---|---|
| Inherit the Size | Use Numeric Values | Use MATLAB Expressions | |
| Local | Only in charts that use MATLAB as the action language | Yes | Yes |
| Constant | No | Yes | Yes |
| Parameter | Yes | Yes | Yes |
| Input | Yes | Yes | Yes |
| Output | Yes | Yes | Yes |
| Data store memory | Yes | No | No |
To configure a Stateflow data object to inherit its size from the corresponding Simulink signal or its definition in the chart, specify a size of –1.
After you simulate or build your model, you can find the inherited size of the data in the Model
Explorer, under the Compiled Size column.
Charts cannot inherit data sizes from Simulink frame-based signals. For more information, see Sample- and Frame-Based Concepts (DSP System Toolbox).
When you specify data size by entering a numeric value, follow these guidelines:
To specify a scalar, enter 1 or leave the field blank.
To specify an n-by-1 column vector, enter
n.
To specify a 1-by-n row vector, enter [1
.n]
To specify an n-by-m matrix, enter
[.n
m]
To specify an n-dimensional array, enter
[, where
d1
d2 ⋯
dn]di is the size of the
ith dimension.
In charts that use C as the action language, one-dimensional Stateflow vectors are compatible with Simulink row or column vectors of the same size. For example, a Stateflow input data of size 3 is compatible with a Simulink row vector of size [1 3] or a column vector of size [3
1].
You can specify data size by entering a MATLAB expression that evaluates to one of the size specifications described in Specify Data Size by Using Numeric Values. These guidelines also apply:
Expressions can contain a mix of numeric values, constants, parameters, variables, arithmetic operations, and calls to MATLAB functions.
Expressions that specify the size of a dimension must evaluate to a positive integer value.
If the expression contains an enumerated value, you must include the type prefix for
consistency with MATLAB naming rules. For example, Colors.Red is valid but
Red is not. For more information, see Notation for Enumerated Values.
You cannot use a MATLAB expression to:
Specify inherited data size. Do not use expressions that evaluate to
-1.
Specify the size of Stateflow input data that accepts frame-based data from Simulink. For more information, see Sample- and Frame-Based Concepts (DSP System Toolbox).
These examples are valid MATLAB expressions for specifying data size in your chart:
K+3, where K is a chart-level Stateflow constant or parameter.
N/2, where N is a variable in the MATLAB base workspace.
[P Q], where P and Q are
Simulink parameters. Charts that use C as the action language propagate these symbolic
dimensions throughout the model. See Propagate Symbolic Dimensions of Stateflow Data.
2*Colors.Red, where Red is an enumerated value of
type Colors.
size(u), where u is a chart-level variable. The
function size enables you to specify the size of one
data object based on the size of another data object. This type of expression is useful in a
library chart that you reuse with data of different sizes. In other situations, you can
improve the clarity of your chart by avoiding the size function and
specifying the size of the data directly.
[fi(2,1,16,2) fi(4,1,16,2)]. This expression specifies a data size of
[2 4] by calling the function fi. This function returns signed fixed-point numbers with a word length of 16
and a fraction length of 2.
When a model contains multiple variables with identical names, the variable with the highest priority is used to specify size.
| Priority | Variable |
|---|---|
| 1 | Mask parameter |
| 2 | Model workspace variable |
| 3 | MATLAB base workspace variable |
| 4 | Stateflow data |
To avoid confusion, do not specify data size by using a variable name that you define in multiple levels of your model.
When you select the model configuration parameter Allow symbolic dimension specification, charts that use C as the action language can propagate the symbolic dimensions of Stateflow data throughout the model. If you have Embedded Coder®, the symbolic dimensions go into the generated code for ERT targets. Specify the size of the symbolic dimensions by using Simulink parameters with one of these storage classes:
Define or ImportedDefine with a
specified header file
CompilerFlag
A user-defined custom storage class that defines data as a macro in a specified header file
For more information, see Allow symbolic dimension specification (Simulink) and Implement Dimension Variants for Array Sizes in Generated Code (Embedded Coder).
Stateflow charts that use MATLAB as the action language do not support symbolic dimension propagation. To specify data size by using Simulink parameters, clear the Allow symbolic dimension specification check box.