SNR vs Amplitude plot for ECG Lead

Hello,

How to plot the figure SNR vs Amplitude for each ECG Lead separately:

%----available amplitudes

amplitudes = {'0.05', '0.10', '0.15', '0.20', '0.25', '0.30', '0.35',...

'0.40', '0.45', '0.50', '1.00', '1.50', '2.00', '2.50', '3.00',...

'3.50', '4.00', '4.50', '5.00', '5.50' }

%heartRates = {'30bpm', '40bpm', '45bpm', '60bpm', '80bpm', '90bpm', '100bpm'}

%heartRates = {'120bpm', '140bpm', '160bpm', '180bpm', '200bpm', '220bpm',...

% '240bpm', '260bpm', '280bpm', '300bpm'}

Fs = 1000;

s = struct;

% Build table

T = table();

SNR = {}

Leads = ["I" "II" "V_"+(1:6)];

ECGLeads = {ecgData.leadI, ecgData.leadII,...

ecgData.V1, ecgData.V2, ecgData.V3,...

ecgData.V4, ecgData.V5, ecgData.V6};

%----get amplitude/heart rate parameter from text file

file = fullFileName

field=textread(file,'%s',7,'delimiter','\n')

%-------for each amplitude parameters

for kleads = 1:length(ECGLeads)

for iamp = 1:length(amplitudes)

if (find(~cellfun(@isempty,strfind(field,amplitudes{iamp}))==true))

% Define parameters

total_samples = size(rawData,1);

sampling_frequency = 1000; % in Hz

duration = 3; % in seconds

% Generate a time vector for the entire signal

t = (0:total_samples-1) / sampling_frequency;

% Generate a e sigsamplnal (for example, a sine wave)

signal = ECGLeads{kleads}; %

% Extract sample of signal

sample_duration = duration; % in seconds

sample_samples = sample_duration * sampling_frequency;

sample_signal = signal(1:sample_samples);

sample_time = t(1:sample_samples);

sample_ecg{kleads} = sample_signal;

%s.(amplitudes{iamp}).(sample_ecg{kleads}) = sample_signal;

%calculate snr

SNR{iamp} = calc_snr(sample_ecg{kleads}, Fs)

end%iamp

end%if

tiledlayout(2, 4, TileIndexing='columnmajor')

for iamp = 1:length(amplitudes)

% snr_Min = min(cell2mat(SNR{:}));

% snr_Max= min(cell2mat(SNR));

% sample_snr;

sample_amplitude = vertcat(amplitudes{:});

nexttile

plot(amplitudes, SNR{iamp});

xlabel('Amplitude (mV)');

ylabel('SNR (dB)');

title(Leads{kleads}, [amplitudes, SNR ]);

% xlim([0 3])

% %ylim([-4.5e-03 50e-04])

% ylim([snr_Min snr_Max])

output_fig_snr = [path_data_fig, Leads{kleads},'.fig']

output_fig_snr_jpg = [path_data_fig, Leads{kleads},'.jpg']

saveas(gcf, output_fig_snr, 'fig')

saveas(gcf, output_fig_snr_jpg, 'jpg')

end %iamp

end %if amp

end %kleads

Answer 1

[Raghava S N]

Hi @Elzbieta,

To plot the SNR vs Amplitude graph for each lead separately, you may follow the below steps.

• Move this command -

tiledlayout(2, 4, 'TileIndexing', 'columnmajor'); 

before the for loop -

for kleads = 1:length(ECGLeads) 

The “tiledlayout” function only needs to be called once to declare a tiled figure. For more information about the “tiledlayout” function, refer to this link - https://www.mathworks.com/help/matlab/ref/tiledlayout.html#:~:text=polarscatter(theta%2Crho)-,Reconfigure%20Content%20in%20Previous%20Tile,-Open%20in%20MATLAB.

• A for loop is not required to call the "plot" function, as the “plot” function is vectorized and can take vectors as inputs to plot. For more information about “plot”, refer to this link - https://www.mathworks.com/help/matlab/ref/plot.html#mw_6748a9ec-33eb-483b-b8f1-919954dfae40:~:text=x%2Dcoordinates-,scalar%20%7C%20vector%20%7C%20matrix,-Y%20%E2%80%94%20y. For vectorization in MATLAB, refer to this link - https://www.mathworks.com/help/matlab/matlab_prog/vectorization.html.
• Convert the amplitude vector to double using the “str2double” function, and the SNR cell array to a vector using the “cell2mat” function. The documentation for “str2double” can be found in this link - https://www.mathworks.com/help/matlab/ref/str2double.html. Refer to this link for more information about the “cell2mat” function - https://www.mathworks.com/help/matlab/ref/cell2mat.html. This is because, the “plot” function takes scalar, vector or matrices as the data to be plotted. Use a modified plot command instead in the for loop -

for kleads = 1:length(ECGLeads)  

after SNR is calculated for all amplitudes-

plot(cellfun(@str2double, amplitudes), cell2mat(SNR)) 

Hope this helps!

Answer 2

[Peter Perkins]

Elzbieta, I have not read your code closely but it seems very likely that stackedplot on a table or timetable will do what you want.