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errpdf

Probability density function of quantization error

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Syntax

[f,x] = errpdf(q)
f = errpdf(q,x)

Description

[f,x] = errpdf(q) returns the probability density function f evaluated at the values in x. The vector x contains the uniformly distributed random quantization errors that arise from quantizing a signal by quantizer object q.

f = errpdf(q,x) returns the probability density function f evaluated at the values in vector x.

Note

The results are not exact when the signal precision is close to the precision of the quantizer.

Examples

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Open Live Script
q = quantizer('nearest',[4 3]);
[f,x] = errpdf(q);
subplot(211)
plot(x,f)
title('Computed PDF of the quantization error.')

Figure contains an axes object. The axes object with title Computed PDF of the quantization error. contains an object of type line.

The output plot shows the probability density function of the quantization error. Compare this result to a plot of the sample probability density function from a Monte Carlo experiment:

 r = realmax(q);
      u = 2*r*rand(10000,1)-r;  % Original signal
      y = quantize(q,u);        % Quantized signal
      e = y - u;                % Error
      subplot(212)
      hist(e,20)
      gca.xlim = [min(x) max(x)];
      title('Estimate of the PDF of the quantization error.')

Figure contains 2 axes objects. Axes object 1 with title Computed PDF of the quantization error. contains an object of type line. Axes object 2 with title Estimate of the PDF of the quantization error. contains an object of type patch. This object represents e.

Version History

Introduced in R2008a

See Also

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