I have extracted the S-T segment from an ECG signal. Now I want to retain only T-waves.
For that I want to detect curved lines and discard the S segment.
You can try looking at the zero crossings of the second derivative of the S-T segment to find the border between the S and T waves.
Alternatively you might be able to use shape matching by using a small annotated set of reference T-waves and aligning them with the T-wave in the S-T segment by finding the position with maximum cross correlation.
Zero crossings of second derivative suggested by Michael Rooijakkers are too noisy and will produce jitter. His second suggestion of 'shape matching' is better.
First and second derivatives together can tell you shape and curve trends. But, you must take into account for the fact that derivatives intrinsically act as high pass filters and therefore they reduce the Signal-to-noise ratio. May be it would be necessary to smooth the signal before taking the derivative
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