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

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Georges Theodosiou
Georges Theodosiou 2021 年 1 月 5 日
編集済み: Georges Theodosiou 2021 年 1 月 5 日
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)

採用された回答

Mischa Kim
Mischa Kim 2021 年 1 月 5 日
編集済み: Mischa Kim 2021 年 1 月 5 日
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).
  2 件のコメント
Georges Theodosiou
Georges Theodosiou 2021 年 1 月 5 日
編集済み: Georges Theodosiou 2021 年 1 月 5 日
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
Mischa Kim 2021 年 1 月 5 日
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.

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