function     qplot(s, nbits, mu, ncases)%QPLOT    for plotting dependence of signal-to-noise ratio%-----           on decreasing signal level%%   Usage:   qplot(s, nbits, mu, ncases)%%             s : input test signal%         nbits : number of bits in quantizer%            mu : mu-law compression parameter%        ncases : number of cases to plot%%  NOTE: assumes ROUNDING for quantizer%        and requires user-written MULINV and SNR%%  see also MULAW and FXQUANT%---------------------------------------------------------------% copyright 1994, by C.S. Burrus, J.H. McClellan, A.V. Oppenheim,% T.W. Parks, R.W. Schafer, & H.W. Schussler.  For use with the book% "Computer-Based Exercises for Signal Processing Using MATLAB"% (Prentice-Hall, 1994).%---------------------------------------------------------------P = zeros(ncases,2);x = s;for i=1:ncases   sh = fxquant(x, nbits, 'round', 'sat');   P(i,1) = (i-1)+sqrt(-1)*snr(sh,x);   y = mulaw(x, mu);   yh = fxquant(y, nbits, 'round', 'sat');   xh  =mulawinv(yh, mu);   P(i,2) = (i-1)+sqrt(-1)*snr(xh,x);   x = x/2;endplot(P)title(['SNR for ', num2str(nbits), '-bit Uniform and ',...         num2str(mu), '-Law Quantizers'])xlabel('power of 2 divisor');   ylabel('SNR in dB')