noisegen noise generation (obsolete)

## Syntax

    b = noisegen(pas, Tmax, sig)

## Arguments

pas

  real scalar, the time increment

Tmax

  real scalar, the final time of the interval of noise generation

sig

  real scalar, the standard deviation of the noise

## Description

`noisegen()` is obsolete. It will be removed from Scilab 6.1.x. Please use grand() instead. Examples (clearer, shorter, and more powerful) follow:

100 10-point wide steps with random amplitudes of normal distribution of mean 1 and standard deviation 0.7:

                u = grand(1,100,"nor",1,0.7) .*. ones(1,10);
                clf, plot(u);

40 15-point wide steps with random amplitudes of uniform distribution in [1 3], with initial level 0.5 and final level hold:

                width = 15;
                u = grand(1,40, "unf", 1, 3) .*. ones(1,width);
                u = [ones(1,8*width)*0.5, u, ones(1,5*width)*u($)];
                clf, plot(u);

`noisegen()` generates a Scilab function `b = Noise(t)` where `Noise(t)` is a piecewise constant function (constant on `[k*pas, (k+1)*pas]`). The value on each constant interval are random values from i.i.d Gaussian variables of standard deviation `sig`. The function is constant for `t <= 0` and `t >= Tmax`.

Note: Random number generator functions such as rand and grand are another alternative to generate noises from a wide variety of probability distribution (see example 2 below).

## Examples

Example #1: noisegen()

    noisegen(0.5, 30, 1.0);
    x = -5:0.01:35;
    y = feval(x, Noise);
    plot(x, y);

noisegen(0.5, 30, 1.0); x = -5:0.01:35; y = feval(x, Noise); plot(x, y);

Example #2: rand()

    // Plot a zero mean gaussian white noise with the variance 1.
    // To use a different variance, multiply rand() by the square root of the variance.
    t = 0:.5:30;
    sig = 1; // Standard deviation of the white gaussian noise
    noise = sig*rand(t, "normal");
    plot2d2(t, noise);

t = 0:.5:30; sig = 1; noise = sig*rand(t, "normal"); plot2d2(t, noise)

## See also

- rand
- grand

## History

6.1.0 noisegen() is obsolete. It will be removed from Scilab 6.1.x. Please replace it with grand() and .*.