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Fcn - Apply specified expression to input

Library

User-Defined Functions

Description

The Fcn block applies the specified mathematical expression to its input. The expression can be made up of 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, fabs, floor, hypot, ln, log, log10, pow, power, rem, sgn, 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.

Data Type Support

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

Parameters and Dialog Box

Expression

The mathematical expression applied to the input. Expression components are listed above. The expression must be mathematically well formed (i.e., matched parentheses, proper number of function arguments, etc.).

Note   You cannot tune the expression during accelerated-mode simulation (see Accelerating Models), in referenced models executing in Accelerator mode (see Referencing a Model, or in generated code. The Fcn block does not support custom storage classes. See Creating and Using Custom Storage Classes.

Sample time (-1 for inherited)

Specify the time interval between samples. To inherit the sample time, set this parameter to -1. See How to Specify the Sample Time in the online documentation for more information.

Characteristics

Direct Feedthrough	Yes
Sample Time	Inherited from driving block
Scalar Expansion	No
Dimensionalized	No
Zero Crossing	No

Extract Bits

First-Order Hold

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