Index exceeds matrix dimensions. Exsample.m

I keep running into the same error for my functions. The error and functions (uniquan.m and sampandquant.m) are shown below:

>> Exsample

Index exceeds the number of array elements (4).

Error in uniquan (line 19)

q_out=q_level(qindex); % use index vector to generate output

Error in sampandquant (line 21)

[sq_out,Delta,SQNR]=uniquan(s_out,L);

Error in Exsample (line 12)

[s_out,sq_out,sqh_out,Delta,SQNR]=sampandquant(xsig,16,td,ts);

Here is my function:

% (Exsample.m)

% Example of sampling, quantization and zero-order hold

clear;clf;

td=0.002; %origional sampling rate 500 Hz

t=[0:td:1.]; %time interval of 1 second

xsig=sin(2*pi*t)-sin(6*pi*t); % 1Hz+3Hz sinusoids

Lsig=length(xsig);

ts=0.02; %new sampling rate = 50Hz.

Nfactor=ts/td;

% send the signal through a 16-level uniform quantizer

[s_out,sq_out,sqh_out,Delta,SQNR]=sampandquant(xsig,16,td,ts);

% receive 3 signals

% 1. sampled signal s_out

% 2. sampled and quantized signal sq_out

% 3. sampled, quantized, and zero-order hold signal sqh_out

%

% Calculate the Fourier Transfoms

Lfft=2^ceil(log2(Lsig)+1);

Fmax=1/(2*td);

Faxis=linspace(-Fmax,Fmax,Lfft);

Xsig=fftshift(fft(xsig,Lfft));

S_out=fftshift(fft(s_out,Lfft));

And I'm drawing from:

% (uniquan.m)

function [q_out,Delta,SQNR]=uniquan(sig_in,L)

% Usage

% [q_out,Delta,SQNR]=uniquan(sig_in,L)

% L - number of uniform quantization levels

% sig_in - input signal vector

% Function outputs:

% q_out - quantized output

% Delta - quantization interval

% SQNR - actual signal to quantization noise ratio

sig_pmax=max(sig_in); % finding the positive peak

sig_nmax=min(sig_in); % finding the negative peak

Delta=(sig_pmax-sig_nmax)/L; % quantization interval

q_level=sig_nmax+Delta/2:sig_pmax-Delta/2; % define Q-levels

L_sig=length(sig_in); % find signal length

sigp=(sig_in-sig_nmax)/Delta+1/2; % convert into 1/2 to L+1/2 range

qindex=round(sigp); % round to 1,2, ... L levels

qindex=min(qindex,L); % eliminate L+1 as a rare possibility

q_out=q_level(qindex); % use index vector to generate output

SQNR=20*log10(norm(sig_in)/norm(sig_in-q_out)); % actual SQNR value

end

And:

% (sampandquant.m)

function [s_out,sq_out,sqh_out,Delta,SQNR]=sampandquant(sig_in,L,td,ts)

% Usage

% [s_out,sq_out,sqh_out,Delta,SQNR=sampandquant(sig_in,L,td,ts)

% L - number of uniform quantization levels

% sif_in - input signal vector

% td - origional signal sampling period of sig_in

% ts - new sampling period

% NOTE: td*fs must be a positive integer;

% Function outputs:

% s_out - sampled output

% sq_out - sample-and-quantized output

% sqh_out - sample, quantize, and hold output

% Delta - quantization interval

% SQNR - actual signal to quantization noise ratio

if (rem(ts/td,1)==0)

nfac=round(ts/td);

p_zoh=ones(1,nfac);

s_out=downsample(sig_in,nfac);

[sq_out,Delta,SQNR]=uniquan(s_out,L);

s_out=upsample(s_out,nfac);

sqh_out=kron(sq_out,p_zoh);

sq_out=upsample(sq_out,nfac);

else

warning('Error! ts/td is not an integer!')

s_out=[];sq_out=[];sqh_out=[];Delta=[];SQNR=[];

end

end

[KSSV]

This error occurs when you try to extract more number of elemnts than present in an array.

Example:

A = rand(1,10);
A(1)   % no error
A(5)   % no error 
A(10)   % no error 
A(11)   % error as there are only 10 elements in A.