Peak detection not detecting any peaks

I'm trying to find peaks in an ECG signal, I normalized it and tried to detect the peaks above multiple thresholds, but it seams that it only detects low peaks and not high peaks. Here is a picture of a sample signal window with the threshold set to 0.6

and here is it with the threshold set to 0.2

It seems like the highest threshold that I can put is 0.2, anything above is not detectable. Here is my findpeaks call:

 [~,locs] = findpeaks(v,'MinPeakHeight',resp2);

where resp2 is the threshold (0-1) values. When no peaks are detected, I get the following warning:

if true
  Warning: Invalid MinPeakHeight. There are no data points greater than MinPeakHeight. 
> In findpeaks>removePeaksBelowMinPeakHeight (line 373)
In findpeaks (line 139)
In autodetection3 (line 39) 
end

Thanks

Answer 1

[David Ding]

Hi Isra,

Please check the raw data to ensure that the peaks near 1 is actually present in the data series. If so, you may try to have "findpeaks" detect these points by calling:

findpeaks(v, 'Threshold', 0.5);

This will only detect the highest points as they are at least 0.5 above their neighboring samples.

Thanks,

David

[isra]

Hi david I've checked the data, and I already normalize every segment of data before applying peak detection on it. I found peaks at 0.9 amplitude but for some reason they are not detected. I also tried what you suggested and I got no peaks detected even with very low thresholds. Here is how I called the function.

    [Pks,locs]= findpeaks(v, 'threshold', 0.5)