Modulate a sine wave after quantizing it

Help! I am trying to modulate a sine wave after quantizing it, but keep getting an error. =================================

t = [0:.1:2*pi]; % Times at which to sample the sine function
sig = sin(t); % Original signal, a sine wave
partition = [-1:2/15:1]; % Length 15, to represent 16 intervals
codebook = [-1.2:2/15:1]; % Length 16, one entry for each interval
[index,quants] = quantiz(sig,partition,codebook); % Quantize.
plot(t,sig,'x',t,quants,'.')
legend('Original signal','Quantized signal');
axis([-.2 7 -1.2 1.2])
M=16;
y=qammod(quants,M)

==============

??? Error using ==> qammod at 39

Elements of input X must be integers in the range [0, M-1].

>>

I checked the max and min value of quants and found it to be:

>> max(quants)= 0.8000

>> min(quants)= -1

Is there some way i can scale quants so I get in the specified range?

Answer 1

[Walter Roberson]

No. You need to fix your codebook. Your codebook must be integers from 0 to M-1 .

[jessica david]

yes, it works that time, but then the values of index = values of quants, i think some info is getting lost in this process. i used codebook = [0:1:15]

[Walter Roberson]

You haven't read the quantiz documentation carefully enough, which has been the source of your problem for several days. The last quantization index will only be used if the signal *exceeds* the last partition parameter, which has never been the case in your calculation as your maximum signal value _equals_ the last partition parameter.