Finding Min and Max of a sinusoidal function

Hi,

So I have the following code and I want to find the min and max of the function. I tried using 'xmin' and 'ymin' but it outputs all of the values instead of the ones I am looking for. Based off the plot I should be getting 4 xmin and 4ymin points as well as 3xmax and 3ymax points.

Anything would help! Thanks.

[Walter Roberson]

You define

fv = 1:n;

What is it that you expect

minx = min(fv,fv(:,1))

to return?

Answer 1

[Star Strider]

I note that you’re using the code change I suggested, even though you did not Accept my previous Answer.

If you have R2017a or later, you can use the islocalmax (link) and the related islocalmin (linked to in that page) functions:

Try this instead:

min_y = find(islocalmin(TL));
max_y = find(islocalmax(TL));

The correspoinding ‘f’ values are ‘fv(min_y)’ and ‘fv(max_y)’.

If you don’t have those functions and do have the Signal Processing Toolbox, use the findpeaks function instead.

Answer 2

[Walter Roberson]

findpeaks(x,y) for the maxima, and findpeaks(x,-y) for the minima.