Fixed-Point Toolbox™

errpdf - Probability density function of quantization error

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

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

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);set(gca,'xlim',[min(x) max(x)])
      title('Estimate of the PDF of the quantization error.')

See Also

errmean, errvar, quantize

errorbar

errvar