How do I save data from a fprintf loop?

Hi,

I have this bit of code, that takes an input as string (usually something like 'hello'), converts it to its binary equiv and then encodes it, then outputs it using the following:

fprintf(['\nDecoded Message = %2d\n   Coded: Error rate = %1.2f, ' ...
        'Number of errors = %d\n'], ...
        Bin(ii),errStats(1),errStats(2));

But I'm unsure how to extract the data generated from this and save it in an array, so that I can use it elsewhere.

For context here is the rest of the code it runs off:

for ii = 1:1:N
    dpskdemod = comm.DPSKDemodulator(8,pi/4);
     dpskdemod2 = comm.DPSKDemodulator(M);
    for counter = 1:numframes
        data = randi([0 1],cfgLDPCEnc.NumInformationBits,1,'int8');
        % Transmit and receive with LDPC coding
        encodedData = ldpcEncode(data,cfgLDPCEnc);
        reshape(encodedData, 1, []);
        modSignal = dpskmod(encodedData);
        recievedSignal = awgn(modSignal,1);
        demodSignal = dpskdemod(recievedSignal);
        recievedBits = ldpcDecode(demodSignal,cfgLDPCDec,maxnumiter);
        errStats = ber(data,recievedBits);

         % Transmit and receive with no LDPC coding
        noCoding = dpskmod2(data);
        rxNoCoding = awgn(noCoding,Bin(ii));
        rxBitsNoCoding = dpskdemod2(rxNoCoding);
        errStatsNoCoding = ber2(data,int8(rxBitsNoCoding));
     
    end

Thank you,

Connor

Answer 1

[dpb]

msgs=string(N,1);
for ii=1:N
  ....
  msgs(ii)=compose(['\nDecoded Message = %2d\n   Coded: Error rate = %1.2f, ' ...
        'Number of errors = %d\n'], Bin(ii),errStats(1),errStats(2));
  fprintf(msgs(ii))
end

to save the actual text itself; not clear just what you intend by " how to extract the data generated from this ".

If it's just the data itself, then a struct array might be the ticket...

for ii=1:N
  ....
  fprintf(['\nDecoded Message = %2d\n   Coded: Error rate = %1.2f, ' ...
        'Number of errors = %d\n'], Bin(ii),errStats(1),errStats(2));
  msgs(ii).Bin=Bin(ii);
  msgs(ii).Err=errStats;
end

to save the data itself as a struct array.

[Connor Baker]

Hi! Thank you for answering.

Sorry, I should've made it more clear.

When I say extract, what I mean is that the code runs a loop which spits out a bunch of numbers, which I want to be able to access so I can plot it using stairs (As it should be 1's and 0's).

In its current form, it doesn't seem to save it, atleast in the format I want.

I tried your two lots of code and it doesn't seem to let me access it in that way. Maybe I'm doing something wrong.

I'll provide the whole section of code as it might provide a better clarity of what I want. When you run it, the output has a 'decoded message' in the command window, its the numbers that follow after that (1's and/or 0's) as opposed to the error rate. I hope that makes sense.

%Clearing the workspace and command window
clear;
clc;
close all;

% Getting input from user
%A = input("what is your message? ", 's');
A='hello';      % input a string so will run -- dpb


% Convert input into Binary, without array form
Bin = reshape(dec2bin(A, 8).'-'0',1,[]);
N = length(Bin);
Binx = reshape(Bin,N,[]);
X = ['Your message "', A, '" has now been converted to binary: '];
disp(X);

Your message "hello" has now been converted to binary: 

fprintf('%d',Bin); % Shows the binary representation of the message

0110100001100101011011000110110001101111

% Setting Parameters for binary to digital

% For the message
Fs = 1e4;                   % Sampling Frequency (12MHz)
Fc = 48000;
Ts = 1/Fs;                  % Sampling Period
f = 10^3;                   % Bit rate
T = 1/f;                    % Bit period
t1 = 0:T:(N-1)*T;           % Time period
t2 = 0:Ts:T-Ts; 
Pc1 = pi;             % Carrier phase for binary input '1' - 180° Phase 
Pc2 = 0;              % Carrier phase for binary input '0' 
Ac = 1;               % Carrier amplitude for binary input  
h = 1;                % Signal fading 
w = 0;                % Noise

% Displaying the signal using stairs 
figure('Name','DPSK Modulation and Demodulation','NumberTitle','off');
subplot(3,1,1);
stairs(t1, Bin,'b','LineWidth',2);
grid on;
axis([0 (N-1)*T -1 2]);
xlabel('Time(Sec)');
ylabel('Amplitude');
title('Digital Message Signal');

% ----- LDPC Code Channel Encoder (Error Correction Scheme) -------
% Parameters for Encoding/Decoding
blockSize = length(Bin);
pcmatrix = ldpcQuasiCyclicMatrix(blockSize,Bin);
cfgLDPCEnc = ldpcEncoderConfig(pcmatrix);
cfgLDPCDec = ldpcDecoderConfig(pcmatrix);
M = 8; %  Modulation order DPSK has powers of 2
numframes = 10;
maxnumiter = 10;
ber = comm.ErrorRate;
ber2 = comm.ErrorRate;
dpskmod = comm.DPSKModulator(8,pi/4);
dpskmod2 = comm.DPSKModulator(M);


for ii = 1:1:N
    dpskdemod = comm.DPSKDemodulator(8,pi/4);
     dpskdemod2 = comm.DPSKDemodulator(M);
    for counter = 1:numframes
        data = randi([0 1],cfgLDPCEnc.NumInformationBits,1,'int8');
        % Transmit and receive with LDPC coding
        encodedData = ldpcEncode(data,cfgLDPCEnc);
        reshape(encodedData, 1, []);
        modSignal = dpskmod(encodedData);
        recievedSignal = awgn(modSignal,1);
        demodSignal = dpskdemod(recievedSignal);
        recievedBits = ldpcDecode(demodSignal,cfgLDPCDec,maxnumiter);
        errStats = ber(data,recievedBits);

         % Transmit and receive with no LDPC coding
        noCoding = dpskmod2(data);
        rxNoCoding = awgn(noCoding,Bin(ii));
        rxBitsNoCoding = dpskdemod2(rxNoCoding);
        errStatsNoCoding = ber2(data,int8(rxBitsNoCoding));
     
    end

  

    fprintf(['\nDecoded Message = %2d\n   Coded: Error rate = %1.2f, ' ...
        'Number of errors = %d\n'], ...
        Bin(ii),errStats(1),errStats(2));


   
    fprintf(['Noncoded: Error rate = %1.2f, ' ...
        'Number of errors = %d\n'], ...
        errStatsNoCoding(1),errStatsNoCoding(2))


end

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 8609

Noncoded: Error rate = 0.71, Number of errors = 11052

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 17098

Noncoded: Error rate = 0.70, Number of errors = 21713

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 25730

Noncoded: Error rate = 0.69, Number of errors = 32304

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 34401

Noncoded: Error rate = 0.70, Number of errors = 43435

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 42967

Noncoded: Error rate = 0.69, Number of errors = 54078

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 51506

Noncoded: Error rate = 0.70, Number of errors = 65300

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 60038

Noncoded: Error rate = 0.70, Number of errors = 76558

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 68572

Noncoded: Error rate = 0.70, Number of errors = 87712

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 77209

Noncoded: Error rate = 0.70, Number of errors = 98914

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 85755

Noncoded: Error rate = 0.70, Number of errors = 109516

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 94467

Noncoded: Error rate = 0.70, Number of errors = 120158

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 102966

Noncoded: Error rate = 0.70, Number of errors = 131324

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 111503

Noncoded: Error rate = 0.70, Number of errors = 142401

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 120044

Noncoded: Error rate = 0.70, Number of errors = 152998

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 128649

Noncoded: Error rate = 0.70, Number of errors = 164176

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 137099

Noncoded: Error rate = 0.70, Number of errors = 174819

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 145716

Noncoded: Error rate = 0.70, Number of errors = 186037

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 154317

Noncoded: Error rate = 0.70, Number of errors = 196639

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 162867

Noncoded: Error rate = 0.70, Number of errors = 207410

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 171538

Noncoded: Error rate = 0.70, Number of errors = 218533

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 180069

Noncoded: Error rate = 0.70, Number of errors = 229238

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 188578

Noncoded: Error rate = 0.70, Number of errors = 239827

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 197126

Noncoded: Error rate = 0.70, Number of errors = 250974

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 205654

Noncoded: Error rate = 0.70, Number of errors = 262155

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 214226

Noncoded: Error rate = 0.70, Number of errors = 273301

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 222729

Noncoded: Error rate = 0.70, Number of errors = 283978

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 231380

Noncoded: Error rate = 0.70, Number of errors = 294738

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 239985

Noncoded: Error rate = 0.70, Number of errors = 305956

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 248585

Noncoded: Error rate = 0.70, Number of errors = 316634

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 257114

Noncoded: Error rate = 0.70, Number of errors = 327405

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 265708

Noncoded: Error rate = 0.70, Number of errors = 338513

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 274195

Noncoded: Error rate = 0.70, Number of errors = 349673

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 282761

Noncoded: Error rate = 0.70, Number of errors = 360777

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 291331

Noncoded: Error rate = 0.70, Number of errors = 371420

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 299909

Noncoded: Error rate = 0.70, Number of errors = 382093

Decoded Message =  0
   Coded: Error rate = 0.55, Number of errors = 308475

Noncoded: Error rate = 0.70, Number of errors = 393305

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 317019

Noncoded: Error rate = 0.70, Number of errors = 403883

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 325610

Noncoded: Error rate = 0.70, Number of errors = 414512

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 334104

Noncoded: Error rate = 0.70, Number of errors = 425282

Decoded Message =  1
   Coded: Error rate = 0.55, Number of errors = 342675

Noncoded: Error rate = 0.70, Number of errors = 435911

[dpb]

OK, so I edited the code so it would run -- which numbers are you trying to save, specifically?

[Star Strider]

I may be missing something, however to save the fprintf output, I would be tempted to use fopen to create a file, dupilicate the fprintf calls using that fileID, to write to the file as well as to the Command Window, then fclose when finished.

[dpb]

Well, S-S, I showed him how to save the fprintf data to do whatever with and that didn't satisfy...I don't yet know what it is that he's wanting saved...certainly writing to a file is another way, writing the saved array w/ writearray would do the same w/o the need for explicitly opening/closing a file handle.

[Connor Baker]

I'm trying to save the 1's and 0's that come after the 'Decoded Message'. As that is its own variable, I thought I could grab it like so:

So maybe it would look like

0

1

0

1

0

0

0

1

or 0101001....etc

I do apologise for any confusion, MATLAB is fairly new for me, so I'm trying to learn as much as I can. Thank you both in advance

[dpb]

You've already got it -- it's Bin and is an array already -- that's what was confusing me is that you already have what that is; you're displaying it one array element at a time is all, instead of altogether as you did early on when you plotted it (as the string of 0 and 1).

[Connor Baker]

Ahhh yes! Of course!!

Sorry!!! I'm not sure what was going on. I got very confused with what I was doinh.

I do apoligise for the confusion, and thank you very much for answering and trying to work through my mess.

Much appreciated :)

[dpb]

Ah...thanks for the clarification. It's easy-enough to lose sight of the forest for the trees--been there, done that, many scars to show for having done...