Approximate experimental data from multiple cells

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fig.jpg

Hello. I have several cell arrays with probe data from .mat-file.

I need to find resonance frequencies and q-factors for each of the 1000 inputs, and then estimate (approximate) them. However, the code below provides only 1 value of fres instead of 1000, and no plot for (i, fres) is shown. (I attached a frequency-amplitude plot)

FStart - cell array (1000*1)
FEnd - cell array (1000*1)
Amp - multiarray (1000*100)

for i = 1:1:1000
    f1 = FStart(i):10:FEnd(i);     
    grid on  
    y1 = plot(f1,Amp(i,:)); 
    [maxValue, maxIndex] = max(Amp(i,:)); %find maximum value of amplitude for each i
    [Q_Value, Q_Index] = max(0.5*AmpA2(i,:)); %also tried 0.5*max() and /2
    fres = f1(maxIndex);                %by index of max amplitude value find resonance frequency
    plot(i,fres)                        %plot resonance frequency for each i
    hold on
end

NB: the last FStart value is less than the first FreqEnd value

Futhermore, I try to esteem the Q factor as: Max(frequency on level = 1/2*MaxAmplitude)-Min(frequency on level = 1/2*MaxAmplitude)

fmin = min(f1(Q_Index))
fmax = max(f1(Q_Index))

But it shows fmin = fmax

Could you please tell, what's the problem here?

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Elaine Carroll 2017-7-12

Excuse me, that's f1, too, I'll edit it.

Guillaume 2017-7-12

在 MATLAB Online 中打开

You say that FStart and Fend are cell arrays, yet your code has

f1 = FStart(i):10:FEnd(i);

which would cause an error if they were indeed cell arrays. Are they actually just plain matrices (in this case vectors)?

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Answer 1

Guillaume 2017-7-12

编辑：Guillaume 2017-7-12

在 MATLAB Online 中打开

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But it shows fmin = fmax Well, of course. I don't understand what you're trying to do but you have:

[Q_Value, Q_Index] = max(0.5*AmpA2(i,:))
fmin = min(f1(Q_Index))
fmax = max(f1(Q_Index))

so AmpA2(i, :) is a column vector from which you're taking the maximum and its location Q_index. There is only ever one Q_Index value returned by max. Therefore f1(Q_Index) is a scalar value. The minimum and maximum of a single value is the same: that single value.

Also: see comment to the question, above, about the cell arrays.

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Elaine Carroll 2017-7-12

编辑：Elaine Carroll 2017-7-12

Thank you for the answer. I understand that there was 1 value, I pointed that out. fres(i) instead of fres solved my problem. I was trying to get an array for fres.

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Approximate experimental data from multiple cells

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