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Math Function

Perform mathematical function

Library

Math Operations

Description

The Math Function block performs numerous common mathematical functions.

    Tip   To perform square root calculations, use the Sqrt block.

You can select one of the following functions from the Function parameter list.

FunctionDescriptionMathematical ExpressionMATLAB® Equivalent
exp

Exponential

eu

exp
log

Natural logarithm

ln u

log
10^u

Power of base 10

10u

10.^u
(see power)

log10

Common (base 10) logarithm

log u

log10
magnitude^2

Complex modulus

|u|2

(abs(u)).^2
(see abs and power)

square

Power 2

u2

u.^2
(see power)

pow

Power

uv

power
conj

Complex conjugate

ū

conj
reciprocal

Reciprocal

1/u

1./u
(see rdivide)

hypot

Square root of sum squares

(u2+v2)0.5

hypot
rem

Remainder after division

rem
mod

Modulus after division

mod
transpose

Transpose

uT

u.'
(see Array vs. Matrix Operations)

hermitian

Complex conjugate transpose

uH

u'
(see Array vs. Matrix Operations)

The block output is the result of the operation of the function on the input or inputs. The functions support the following types of operations.

FunctionScalar OperationsElement-Wise Vector and Matrix OperationsVector and Matrix Operations
exp

yes

yes

log

yes

yes

10^u

yes

yes

log10

yes

yes

magnitude^2

yes

yes

square

yes

yes

pow

yes

yes

conj

yes

yes

reciprocal

yes

yes

hypot

yes, on two inputs

yes, on two inputs (two vectors or two matrices of the same size, a scalar and a vector, or a scalar and a matrix)

rem

yes, on two inputs

yes, on two inputs (two vectors or two matrices of the same size, a scalar and a vector, or a scalar and a matrix)

mod

yes, on two inputs

yes, on two inputs (two vectors or two matrices of the same size, a scalar and a vector, or a scalar and a matrix)

transpose

yes

yes

hermitian

yes

yes

The name of the function appears on the block. The appropriate number of input ports appears automatically.

    Tip   Use the Math Function block instead of the Fcn block when you want vector or matrix output, because the Fcn block produces only scalar output.

Data Type Support

The following table shows the input data types that each function of the block can support.

Functionsingledoublebooleanbuilt-in integerfixed point

exp

yes

yes

log

yes

yes

10^u

yes

yes

log10

yes

yes

magnitude^2

yes

yes

yes

yes

square

yes

yes

yes

yes

pow

yes

yes

conj

yes

yes

yes

yes

reciprocal

yes

yes

yes

yes

hypot

yes

yes

rem

yes

yes

yes

mod

yes

yes

yes

transpose

yes

yes

yes

yes

yes

hermitian

yes

yes

yes

yes

All supported modes accept both real and complex inputs, except for reciprocal, which does not accept complex fixed-point inputs.

The block output is real or complex, depending on what you select for Output signal type.

Parameters and Dialog Box

The Main pane of the Math Function block dialog box appears as follows:

Function

Specify the mathematical function. See Description for more information about the options for this parameter.

Output signal type

Specify the output signal type of the Math Function block as auto, real, or complex.

FunctionInput Signal TypeOutput Signal Type
AutoRealComplex

exp, log, 10u, log10, square, pow, reciprocal, conjugate, transpose, hermitian

real

complex

real

complex

real

error

complex

complex

magnitude squared

real

complex

real

real

real

real

complex

complex

hypot, rem, mod

real

complex

real

error

real

error

complex

error

Sample time (-1 for inherited)

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

The Signal Attributes pane of the Math Function block dialog box appears as follows:

    Note   Some parameters on this pane are available only when the function you select in the Function parameter supports fixed-point data types.

Output minimum

Specify the minimum value that the block can output. The default value is [] (unspecified). Simulink® software uses this value to perform:

  • Simulation range checking (see Signal Ranges)

  • Automatic scaling of fixed-point data types

Output maximum

Specify the maximum value that the block can output. The default value is [] (unspecified). Simulink software uses this value to perform:

  • Simulation range checking (see Signal Ranges)

  • Automatic scaling of fixed-point data types

Output data type

Specify the output data type. You can set it to:

  • A rule that inherits a data type, for example, Inherit: Inherit via back propagation

  • The name of a built-in data type, for example, single

  • The name of a data type object, for example, a Simulink.NumericType object

  • An expression that evaluates to a data type, for example, fixdt(1,16,0)

Click the Show data type assistant button to display the Data Type Assistant, which helps you set the Output data type parameter.

See Specify Block Output Data Types for more information.

Lock output data type setting against changes by the fixed-point tools

Select to lock the output data type setting of this block against changes by the Fixed-Point Tool and the Fixed-Point Advisor. For more information, see Use Lock Output Data Type Setting.

Integer rounding mode

Specify the rounding mode for fixed-point operations. For more information, see Rounding. in the Fixed-Point Designer™ documentation.

Saturate on integer overflow
ActionReasons for Taking This ActionWhat Happens for OverflowsExample

Select this check box.

Your model has possible overflow, and you want explicit saturation protection in the generated code.

Overflows saturate to either the minimum or maximum value that the data type can represent.

The maximum value that the int8 (signed, 8-bit integer) data type can represent is 127. Any block operation result greater than this maximum value causes overflow of the 8-bit integer. With the check box selected, the block output saturates at 127. Similarly, the block output saturates at a minimum output value of -128.

Do not select this check box.

You want to optimize efficiency of your generated code.

You want to avoid overspecifying how a block handles out-of-range signals. For more information, see Checking for Signal Range Errors.

Overflows wrap to the appropriate value that is representable by the data type.

The maximum value that the int8 (signed, 8-bit integer) data type can represent is 127. Any block operation result greater than this maximum value causes overflow of the 8-bit integer. With the check box cleared, the software interprets the overflow-causing value as int8, which can produce an unintended result. For example, a block result of 130 (binary 1000 0010) expressed as int8, is -126.

When you select this check box, saturation applies to every internal operation on the block, not just the output or result. Usually, the code generation process can detect when overflow is not possible. In this case, the code generator does not produce saturation code.

Characteristics

Direct Feedthrough

Yes

Sample Time

Specified in the Sample time parameter

Scalar Expansion

Yes, of the input when the function requires two inputs

Dimensionalized

Yes

Multidimensionalized

Yes, for all functions except hermitian and transpose

Zero-Crossing Detection

No

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