max and min in one cycle

Hi everyone

I have a signal, I need to find max and min values for each cycle in this signal.

Let's say we have the signal A which has two cycles:

Signal=[0 -2 -3 -3.5 -3.25 -2.5 -1.75 -1 0 1 1.8 2.6 3.25 3.5 3.25 2.6 1.7 0 -2 -3 -3.5 -3.25 -2.5 -1.75 -1 0 1 1.8 2.6 3.25 3.5 3.25 2.6 1.7 0]

as shown in the attached picture.

I should get for the first cycle -3.5 and 3.25 and the same values for the second cycles.

Thank you in advance

[Walter Roberson]

Perhaps run findpeaks twice, once on Signal and once on -Signal

[Mohanned Al Gharawi]

Thank you for your responding, But I think findpeaks gives us only one value for one signal, while what I want finding max and min values (two values) for the first cycle then the max and min (also two values) for the second cycle and keep going to the last cycle for one signal. Thanks

Answer 1

[Image Analyst]

If you have the Image Processing Toolbox, you can do this:

props = regionprops(Signal < 0, Signal, 'MinIntensity');
minIntensities = [props.MinIntensity]
props = regionprops(Signal > 0, Signal, 'MaxIntensity');
maxIntensities = [props.MaxIntensity]

but I get 3.5 for the maxima. Why are you saying 3.25?

[Mohanned Al Gharawi]

Yes my mistake it must be 3.5, and the code worked. Thank you so much.

Answer 2

[Walter Roberson]

[maxpk, maxloc] = findpeaks(Signal);
[minpk, minloc] = findpeaks(-Signal);
extremevals = [maxpk.', -minpk.'];
extremlocs = [maxloc.', minloc.'];

>> extremevals
extremevals =
                       3.5                      -3.5
                       3.5                      -3.5
>> extremlocs
extremlocs =
    14     4
    31    21

[Mohanned Al Gharawi]

Thanks it works also, I appreciate your help.