Documentation

Fcn

Apply specified expression to input

• Library:
• 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.

Ports

Input

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

Data Types: single | double

Output

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

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