How can I flip the top area of the peak that is going down?

Hi, I would like to flip the part of the peak that goes gown so its pointed upward. I want there to be a space between the data where the top-points are to mark that this was the end-points and that the top peak goes upward instead of downward.. how can you do this?

Answer 1

[Image Analyst]

For one such section, this should work (untested):

peakValue = max(signal);
index1 = find(signal > (peakValue - 0.001), 1, 'first')
index2 = find(signal > (peakValue - 0.001), 1, 'last');
signal(index1:index2) = 2 * peakValue - signal(index1:index2);

[Lizan]

Can you comment on what you are doing in this line:

   2 * peakValue - signal(index1:index2)

[Image Analyst]

It's basically finding the distance between the max (top of the box) and the signal below the top of the box. Maybe if I did it more explicitly like this

delta = abs(peakValue - signal)
% Now add the delta to a vertical offset of peakValue
newSignal = peakValue + delta

but if you do the math you get

newSignal = peakValue + peakValue - signal
newSignal = 2 * peakValue - signal

So that's how I got the formula.