Error Using Integers in MATLAB

Question

James Manns 2024-4-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2112716-error-using-integers-in-matlab

评论： James Manns 2024-4-29

采纳的回答： Harsh

在 MATLAB Online 中打开

How to correct the following error:

Error using +

Integers can only be combined with integers of the same class, or scalar doubles.

Error in Computerassignment5b042824 (line 28)

received_signal_low = modulated_bits + noise_low;

clc;
clear all;
% Task 1: Simulate transmission of lenna.pgm image using BPSK
% Read the image
img = imread('lenna.png');
% Convert image to bits
img_bits = reshape(de2bi(img(:), 8, 'left-msb').', [], 1);
% BPSK modulation
modulated_bits = 2*img_bits - 1;
% Eb/No values in dB
EbNo_low = 0;
EbNo_high = 4;
% Additive White Gaussian Noise (AWGN) channel
SNR_low = 10^(EbNo_low/10);
SNR_high = 10^(EbNo_high/10);
% Generate noise
noise_low = sqrt(1/SNR_low)*randn(size(modulated_bits));
noise_high = sqrt(1/SNR_high)*randn(size(modulated_bits));
% Received signals at low and high SNR
received_signal_low = modulated_bits + noise_low;
received_signal_high = modulated_bits + noise_high;
% BPSK demodulation
demodulated_bits_low = sign(received_signal_low);
demodulated_bits_high = sign(received_signal_high);
% Convert bits back to image
received_img_low = reshape((demodulated_bits_low + 1) / 2, 8, []).';
received_img_high = reshape((demodulated_bits_high + 1) / 2, 8, []).';
% Display images
figure;
subplot(2,2,1);
imshow(img);
title('Original Image');
subplot(2,2,2);
imshow(received_img_low, []);
title('Received Image (0 dB SNR)');
subplot(2,2,3);
imshow(received_img_high, []);
title('Received Image (4 dB SNR)');
% Task 2: Employ a linear error detection code (only detection and no correction)
% Count re-transmission requests at different SNR levels
EbNo_values = [0, 2, 4, 6, 8, 10];
retrans_requests = zeros(size(EbNo_values));
for i = 1:length(EbNo_values)
    SNR = 10^(EbNo_values(i)/10);
    noise = sqrt(1/SNR)*randn(size(modulated_bits));
    received_signal = modulated_bits + noise;
    demodulated_bits = sign(received_signal);
    % Linear error detection code
    % Let's use a simple parity check code
    error_idx = mod(sum(demodulated_bits == -1), 2) == 1;
    if any(error_idx)
        retrans_requests(i) = sum(error_idx);
    else
        break; % No errors, stop transmission
    end
end
% Plot number of retransmission requests against SNR values
figure;
plot(EbNo_values(1:i), retrans_requests(1:i), '-o');
xlabel('Eb/No (dB)');
ylabel('Number of Retransmission Requests');
title('Retransmission Requests vs. SNR');
% Task 3: Use an error correction code using syndrome lookup table
% Error correction code
% Let's use a (7, 4) Hamming code
enc = comm.HammingEncoder;
dec = comm.HammingDecoder;
% Corrected images at 0 dB and 4 dB SNR
corrected_img_low = correct_image(received_signal_low, enc, dec);
corrected_img_high = correct_image(received_signal_high, enc, dec);
% Display corrected images
figure;
subplot(1,2,1);
imshow(corrected_img_low, []);
title('Corrected Image (0 dB SNR)');
subplot(1,2,2);
imshow(corrected_img_high, []);
title('Corrected Image (4 dB SNR)');
% Function to correct image using error correction code
function corrected_img = correct_image(received_signal, enc, dec)
    % BPSK demodulation
    demodulated_bits = sign(received_signal);
    % Perform error detection and correction
    detected_bits = step(dec, demodulated_bits);
    % Convert bits back to image
    corrected_img = reshape((detected_bits + 1) / 2, 8, []).';
end

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James Manns 2024-4-29

James Manns 2024-4-29

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Answer 1

Harsh 2024-4-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2112716-error-using-integers-in-matlab#answer_1449341

在 MATLAB Online 中打开

Hi James,

From what I can gather, you are trying to run the above-mentioned code in MATLAB and are facing an error while using (+) operand.

This error has occured because “modulated_bits” and “noise_low” are of type of uint8 and double respectively, combining them is not possible without matching the data types of the two operands.

Converting “noise_low” to uint8 using the “uint8()” function or “modulated_bits” to double using the “double()” function can resolve this error, please refer to the code below which resolves your issue:

% (in line no. 28) 
received_signal_low = double(modulated_bits) + noise_low; 

Please ensure to match the data types of the variable being updated throughout the subsequent lines.

I hope this helps, thanks!

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Harsh 2024-4-29

编辑：Harsh 2024-4-29

Hi Dyuman,

Apologies for any confusion I may have caused. In the following sentence, I neglected to include: {.... are/ arrays /of type uint8 ....}

"This error has occured because “modulated_bits” and “noise_low” are of type of uint8 and double respectively, combining them is not possible without matching the data types of the two operands. "

"Also, how are you saying that modulated_bits is of data type uint8?"

After running the above mentioned script, "modulated_bits" was stored as an array of type uint8 in my MATLAB desktop.