Asked by Genus
on 15 May 2013

I am having problems with the rate distortion function implemented in matlab. im recieving an error message of

Error in ==> blahut at 9 m=sum(p.*Y); %mathematical expectation of Y

Error in ==> Rate_distort at 18 [R,SNR] = blahut(p,nl,Y');

here is the blahut mfile

function [R,SNR] = blahut(p,nl,Y) %This function computes one point of H(D) for given lambda %D is distortion in dB %p is probability distribution of input sequence %nl=-lambda %Y is approximating set

m=sum(p.*Y); %mathematical expectation of Y sigma2=sum(p.*(Y-m).^2);%variation of Y N=length(p); ry=p; %initialization of distribution r(y) diff=(diag(Y)*ones(N,N)-ones(N,N)*diag(Y)).^2;

A=2.^(-nl*diff); D=diff.*A; flag=1; %%%%%%%%Iterations%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% while flag==1 v=ry*A'; %sum_y r(y)2^(lambda d(x,y)) P=p./v;%p(x)/sum_y r(y)2^(lambda d(x,y)) c=P*A; %c(y) ry=ry.*c; %modified distribution %%%%%%%%Computing thresholds%%%%%%%%%%%%%%%%%%%% TU=-sum(ry.*log2(c)); TL=-max(log2(c)); error=TU-TL; %%%%%%%%%%%%%Stopping rule%%%%%%%%%%%%%%%%%%%%% if error < 10^(-3) flag=0; end d=P*D*ry'; %distortion rate=-nl*d-log2(v)*p'-TL; %rate; end R=rate; SNR=10*log10(sigma2/d);%distortion in dB

Here is my test file with components

N takes in values from 10:10:50

P is the probability distribution in the form of the binomial distribution

theta takes in value in the interval [0 1]

also theta is specified for theta = i/n with i = 0,1,....,n

%% Values for n n=50; %% theta=0:0.5; nVec=10:n; for jdx=1:length(theta) for kdx=1:length(nVec) p(jdx,kdx)=nchoosek(n,nVec(kdx))*((theta)^nVec(kdx))*((1-(theta))^(n-nVec(kdx))); end end %% specifications for rate distortion nl = 0.1; Y = [0 1; 1 0]; %% Blahut algorithm for rate distortion calculation [R,SNR] = blahut(p,nl,Y');

When I type in my disitortion matrix for Y, this is where Im encountering the error

Error in ==> blahut at 9 m=sum(p.*Y); %mathematical expectation of Y

end

I also need to know how to plot the Distortion vs R(D).

Please help with any tips. Thank you very much if true

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## 2 Comments

## Azzi Abdelmalek (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/75861-about-the-rate-distortion-function#comment_149083

How to format your question

## Walter Roberson (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/75861-about-the-rate-distortion-function#comment_149782

There would be an error message just before that. For example it might say something like "matrix dimensions must agree". We need to see that message.