This example shows how to use and configure the `dsp.ArrayPlot`

to
visualize the Central Limit Theorem. This theorem states that the
mean of a large number of independent random variables with finite
mean and variance exhibits a normal distribution.

First, generate uniformly distributed random variables in MATLAB^{®} using
the `rand`

function. Find their
distributions using the `hist`

function.
At the MATLAB command line, type:

numsamples = 1e4; numbins = 20; r = rand(numsamples,1); hst = hist(r,numbins);

Create a new Array Plot object.

hap3 = dsp.ArrayPlot;

Configure the properties of the Array Plot object to plot a histogram.

```
hap3 = dsp.ArrayPlot;
hap3.XOffset = 0;
hap3.SampleIncrement = 1/numbins;
hap3.PlotType = 'Stem';
hap3.YLimits = [0, max(hst)+1];
```

Call the `step`

method to plot the uniform distribution.

step(hap3,hst');

The following Array Plot figure appears, showing a uniform distribution.

Next, calculate the mean of multiple uniformly distributed random
variables. As the number of random variables increases, the distribution
more closely resembles a normal curve. Run the `release`

method
to let property values and input characteristics change. At the MATLAB command
line, type:

release(hap3);

Change the configuration of the Array Plot properties for the display of a distribution function.

```
numbins = 201;
numtrials = 100;
r = zeros(numsamples,1);
hap3.SampleIncrement = 1/numbins;
hap3.PlotType = 'Stairs';
```

Call the `step`

method repeatedly to plot the uniform
distribution.

for ii = 1:numtrials r = rand(numsamples,1)+r; hst = hist(r/ii,0:1/numbins:1); hap3.YLimits = [min(hst)-1, max(hst)+1]; step(hap3,hst'); pause(0.1); end

When the simulation has finished, the Array Plot figure displays a bell curve, indicating a distribution that is close to normal.

The zoom tools allow you to zoom in simultaneously in the directions
of both the *x*- and *y*-axes or
in either direction individually. For example, to zoom in on the distribution
between 0.3 and 0.7, you can use the **Zoom X** option.

To activate the

**Zoom X**tool, select**Tools**>**Zoom X**, or press the corresponding toolbar button ( ). You can determine if the**Zoom X**tool is active by looking for an indented toolbar button or a check mark next to the**Tools**>**Zoom X**menu option.Next, zoom in on the region between 0.3 and 0.7. In the Array Plot window, click on the 0.3-second mark, and drag to the 0.7-second mark. The display reflects this new

*x*-axis setting, as shown in the following figure.

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