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Fcn

Apply specified expression to input

  • Fcn block

Libraries:
Simulink / User-Defined Functions

Description

The Fcn block applies the specified mathematical expression to its input. The expression can include one or more of these components:

  • u — The input to the block. If u is a vector, u(i) represents the ith element of the vector; u(1) or u alone represents the first element.

  • Numeric constants.

  • Arithmetic operators (+ - * / ^).

  • Relational operators (== != > < >= <=) — The expression returns 1 if the relation is true; otherwise, it returns 0.

  • Logical operators (&& || !) — The expression returns 1 if the relation is true; otherwise, it returns 0.

  • Parentheses.

  • Mathematical functions — abs, acos, asin, atan, atan2, ceil, cos, cosh, exp, floor, hypot, log, log10, power, rem, sgn (equivalent to sign in MATLAB®), sin, sinh, sqrt, tan, and tanh.

    Note

    The Fcn block does not support round and fix. Use the Rounding Function block to apply these rounding modes.

  • Workspace variables — Variable names that are not recognized in the preceding list of items are passed to MATLAB for evaluation. Matrix or vector elements must be specifically referenced (e.g., A(1,1) instead of A for the first element in the matrix).

The Fcn block observes the following rules of operator precedence:

  1. ( )

  2. ^

  3. + - (unary)

  4. !

  5. * /

  6. + -

  7. > < <= >=

  8. == !=

  9. &&

  10. ||

The expression differs from a MATLAB expression in that the expression cannot perform matrix computations. Also, this block does not support the colon operator (:).

Block input can be a scalar or vector. The output is always a scalar. For vector output, consider using the Math Function block. If a block input is a vector and the function operates on input elements individually (for example, the sin function), the block operates on only the first vector element.

Limitations

Ports

Input

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The Fcn block accepts and outputs signals of type single or double.

For more information, see Data Types Supported by Simulink in the Simulink® documentation.

Data Types: single | double

Output

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The Fcn block accepts and outputs signals of type single or double.

For more information, see Data Types Supported by Simulink in the Simulink documentation.

Data Types: single | double

Parameters

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Specify the mathematical expression to apply to the input. Expression components are listed above. The expression must be mathematically well-formed (uses matched parentheses, proper number of function arguments, and so on). The expression has restrictions on tunability (see Limitations).

Programmatic Use

Block Parameter: Expr
Type: character vector
Value: mathematical expression
Default: 'sin(u(1)*exp(2.3*(-u(2))))'

Note

This parameter is not visible in the block dialog box unless it is explicitly set to a value other than -1. To learn more, see Blocks for Which Sample Time Is Not Recommended.

Block Characteristics

Data Types

double | single

Direct Feedthrough

yes

Multidimensional Signals

no

Variable-Size Signals

no

Zero-Crossing Detection

no

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced before R2006a

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