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Uniform Random Number

Generate uniformly distributed random numbers

Library

Sources

Description

The Uniform Random Number block generates uniformly distributed random numbers over an interval that you specify. To generate normally distributed random numbers, use the Random Number block.

You can generate a repeatable sequence using any Uniform Random Number block with the same nonnegative seed and parameters. The seed resets to the specified value each time a simulation starts.

Avoid integrating a random signal, because solvers must integrate relatively smooth signals. Instead, use the Band-Limited White Noise block.

The numeric parameters of this block must have the same dimensions after scalar expansion. If you select the Interpret vector parameters as 1-D check box and the numeric parameters are row or column vectors after scalar expansion, the block outputs a 1-D signal. If you clear the Interpret vector parameters as 1-D check box, the block outputs a signal of the same dimensionality as the parameters.

Data Type Support

The Uniform Random Number block accepts and outputs a real signal of type double.

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

Parameters and Dialog Box

Minimum

Specify the minimum of the interval. The default is -1.

Maximum

Specify the maximum of the interval. The default is 1.

Seed

Specify the starting seed for the random number generator. The default is 0.

The seed must be 0 or a positive integer. Output is repeatable for a given seed.

Sample time

Specify the time interval between samples. The default is 0.1. See Specify Sample Time in the Simulink documentation for more information.

Interpret vector parameters as 1-D

If you select this check box and the other parameters are row or column vectors after scalar expansion, the block outputs a 1-D signal. Otherwise, the block outputs a signal of the same dimensionality as the other parameters. For more information, see Determining the Output Dimensions of Source Blocks in the Simulink documentation.

Characteristics

Sample Time

Specified in the Sample time parameter

Scalar Expansion

Yes, of parameters

Dimensionalized

Yes

Multidimensionalized

Yes

Zero-Crossing Detection

No

Algorithm

mcg16807, multiplicative congruential generator

The generator algorithm is identical to the one used in MATLAB® Version 4.0 by the rand and randn functions. For details on the mcg16807 algorithm, see Choosing a Random Number Generator in the MATLAB documentation.

To use other algorithms supported by MATLAB in a Simulink model, generate a set of random numbers in MATLAB, and store the output as a .mat file. Use this .mat file as the random number input for your simulation. For more information, see Creating and Controlling a Random Number Stream. To create multiple independent streams using MATLAB, see Multiple streams

    Note:   Using multiple seeds to generate multiple parallel independent streams for a generator algorithm is not recommended for the mcg16807 algorithm. Instead, use the method described above.

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