mathematical morphology in ecg signal

can someone please tell me the matlab codes for dilating a ecg signal using imdilate function?

Answer 1

[Image Analyst]

Unless an ecg signal is different than any other signal for some reason, the help on imdilate should have explained it. But anyway, try this:

% Make some random data.
ecg = rand(100,1);
% Dilate it.
filtered_ecg = imdilate(ecg, ones(3,1), 'same');

% Plot the signals.
subplot(2,1,1);
plot(ecg, 'b-', 'LineWidth', 2);
grid on;
title('Original ecg signal', 'FontSize', 30);
subplot(2,1,2);
plot(filtered_ecg, 'b-', 'LineWidth', 2);
grid on;
title('Dilated ecg signal', 'FontSize', 30);

% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); % Maximize figure.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off')

Nothing tricky or unusual at all. Since this is just the standard call to imdilate like you'd do for any signal (and probably just what you tried already), you'll have to explain why it's not appropriate for ecg signal. Or maybe dilation is just not really what you want to do???

[Kirthika]

thanks a lot..we got dilated image..

Answer 2

[SMY]

Hello Image Analyst,

I would to ask, what is means by one(3,1) in the coding that you provided below? Is it structuring elements?

% Make some random data. ecg = rand(100,1); % Dilate it. filtered_ecg = imdilate(ecg, ones(3,1), 'same');

[Image Analyst]

It means to make a filter window like this:

1
1
1

So it will be a sliding window that moves down your ecg, which is a column vector, giving you the local max in a 3-by-3 window.

[SMY]

Thank you for the response. But I still have a doubt. How to set that value? Because when I used the same as yours, I got the original signal. It is not change my signal at all.

[Image Analyst]

You're saying that filtered_ecg is the same as the input ecg. That cannot be true unless your signal is completely constant - the same value everywhere.

Obviously, it does not change your original signal and replace your original signal. It makes a copy of your original signal, then dilates it and puts the changed copy into filtered_ecg.

[SMY]

I am very sorry. I made a mistake before. I got the dilated signal now. But can I know how to choose the value for the filter window?

[Image Analyst]

I have no idea. I don't have any idea why you even want to do this or what you want to achieve, in higher sense. You didn't supply the "big picture" at all. I simply told you how to dilate the signal (to find the local max) like you asked.