How to automatically calibrate axes in MATLAB?

Question

So I am doing some ECG analysis in MATLAB and so far I have detected the key features as shown in the figure below :

This is the ground truth :

So how do i replot the first figure such that the x axis ranges from 0 to 10 (as shown in the second image)

I want to do this so that I can measure the time duration between the Q(the red cross) and the S (the peak at the minimum marked with a circle).

So essentially I want to 1) Calibrate 3600 samples into 10 seconds 2) Using the above scaling factor, be able to automatically calibrate any number of samples into the relevant seconds.

Thanks.

Answer 1

How did you plot the first figure? If you did not provide any x-axis, as in plot(ecg) , the x-tick labels will be enumerated consecutevly in intervals of one. If you do know the corresponding time points t of ecg , you can use plot(t, egg); .

Since you know the sampling rate and assume consistent intervals between each data point, you can generate t yourself by t = 10.0 / 3600 * (0 : length(ecg)-1) . This will create an array with length(ecg) elements starting at 0, with 10.0 per 3600 data points, for any length of ecg .

To align the horizontal axis limits more nicely than in the first plot, you can then also use xlim([0, t(end)]) .