about the rate distortion function

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Genus
Genus 2013-5-15
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
  2 个评论
Walter Roberson
Walter Roberson 2013-5-19
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.

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