How can I get the first zero maximum in my program?

Ladies, Gentlemen,

Please let me ask you on how I can get the first zero maximum in following code. I'm beginner in MATLAB. I use b(3) for I see that 3rd element in peaks is the first zero element. But it's bad way. I ask your suggestion for some good way, according to your experience with MATLAB.

I need this code for get fundamental frequencies. I apply my method First Absolute Least Sum.

With regards and friendship, Georges Theodosiou

format short
SamplFreq = 96000;
Segm = (1:9600);

% Harmonics
HarmFreq1 = 150;
HarmPhase1 = 0.2*pi;
HarmAngle1 = Segm*HarmFreq1*2*pi/SamplFreq;
HarmSin1 = sin(HarmAngle1);

HarmFreq2 = 2*HarmFreq1;
HarmPhase2 = 1.2*pi;
HarmAngle2 = Segm*HarmFreq2*2*pi/SamplFreq;
HarmSin2 = sin(HarmAngle2);

HarmFreq3 = 3*HarmFreq1;
HarmPhase3 = 2.2*pi;
HarmAngle3 = Segm*HarmFreq3*2*pi/SamplFreq;
HarmSin3 = sin(HarmAngle3);

Xn = HarmSin1+HarmSin2+HarmSin3;

a = 2000;
Sum = ones(1,a);
for k = 1:a;
    Sum(k) = sum(Xn(1:k));
end
[a,b] = findpeaks(-abs(Sum));
fundFreq = SamplFreq/b(3)

Answer 1

[Mischa Kim]

Georges, you could use something like this to find your first zero:

b(find((abs(a)<1e-12),1))

Of course, this is assuming, for example, that your zeros are sufficiently small/close to zero (I used 1e-12 as a measure).

[Georges Theodosiou]

Mr. Mischa Kim,

Please accept my many thanks for you answered my question and that immidiately. some "zeros" are of the level 1e-13 but some of 1e-7. For example for fundamental frequency (HarmFreq1) 90 Hz, first "zero" is 0.0039 so I put 1e-2. I can work on it.

With regards and friendship, Georges Theodosiou

[Mischa Kim]

Your very welcome. As long as you know how small the "zeros" are you can pick an adequate number to replace the 1e-12 in my code snippet.