MATLAB: Finding the dominant frequency via fourier transform

Question

Hi All,

I have been struggling to find the dominant frequency for a series of data that I have recorded in my experiments. Would be wonderful if you help me how to resolve my issue.

data series:

t=[40:0.1:300.2];

x=[6.54E-06
6.53E-06
6.52E-06
6.54E-06
6.58E-06
6.62E-06
6.65E-06
6.67E-06
6.67E-06
6.66E-06
6.65E-06
6.66E-06
6.69E-06
6.73E-06
6.75E-06
6.73E-06
6.69E-06
6.66E-06
6.65E-06
6.66E-06
6.66E-06
6.64E-06
6.61E-06
6.56E-06
6.51E-06
6.48E-06
6.46E-06
6.47E-06
6.47E-06
6.50E-06
6.53E-06
6.56E-06
6.55E-06
6.52E-06
6.52E-06
6.56E-06
6.62E-06
6.67E-06
6.69E-06
6.70E-06
6.71E-06
6.72E-06
6.74E-06
6.77E-06
6.80E-06
6.82E-06
6.83E-06
6.83E-06
6.82E-06
6.80E-06
6.77E-06
6.75E-06
6.76E-06
6.78E-06
6.77E-06
6.75E-06
6.73E-06
6.73E-06
6.76E-06
6.80E-06
6.83E-06
6.86E-06
6.87E-06
6.87E-06
6.86E-06
6.83E-06
6.83E-06
6.83E-06
6.83E-06
6.83E-06
6.83E-06
6.81E-06
6.79E-06
6.76E-06
6.74E-06
6.73E-06
6.72E-06
6.69E-06
6.65E-06
6.61E-06
6.57E-06
6.53E-06
6.49E-06
6.46E-06
6.45E-06
6.45E-06
6.44E-06
6.44E-06
6.44E-06
6.43E-06
6.43E-06
6.43E-06
6.42E-06
6.43E-06
6.43E-06
6.41E-06
6.41E-06
6.42E-06
6.41E-06
6.38E-06
6.33E-06
6.32E-06
6.33E-06
6.35E-06
6.36E-06
6.36E-06
6.33E-06
6.28E-06
6.23E-06
6.21E-06
6.20E-06
6.21E-06
6.24E-06
6.27E-06
6.30E-06
6.32E-06
6.32E-06
6.29E-06
6.26E-06
6.26E-06
6.28E-06
6.31E-06
6.32E-06
6.32E-06
6.33E-06
6.33E-06
6.32E-06
6.32E-06
6.34E-06
6.35E-06
6.37E-06
6.37E-06
6.34E-06
6.29E-06
6.24E-06
6.20E-06
6.19E-06
6.20E-06
6.22E-06
6.24E-06
6.24E-06
6.23E-06
6.22E-06
6.20E-06
6.18E-06
6.17E-06
6.19E-06
6.23E-06
6.27E-06
6.30E-06
6.31E-06
6.30E-06
6.30E-06
6.32E-06
6.35E-06
6.36E-06
6.37E-06
6.37E-06
6.38E-06
6.37E-06
6.37E-06
6.36E-06
6.37E-06
6.39E-06
6.40E-06
6.40E-06
6.40E-06
6.40E-06
6.37E-06
6.34E-06
6.29E-06
6.26E-06
6.24E-06
6.24E-06
6.23E-06
6.20E-06
6.17E-06
6.14E-06
6.13E-06
6.15E-06
6.19E-06
6.23E-06
6.27E-06
6.30E-06
6.32E-06
6.34E-06
6.33E-06
6.30E-06
6.27E-06
6.27E-06
6.28E-06
6.29E-06
6.31E-06
6.33E-06
6.35E-06
6.37E-06
6.41E-06
6.43E-06
6.44E-06
6.43E-06
6.39E-06
6.33E-06
6.27E-06
6.22E-06
6.19E-06
6.17E-06
6.18E-06
6.20E-06
6.23E-06
6.25E-06
6.27E-06
6.28E-06
6.29E-06
6.27E-06
6.26E-06
6.25E-06
6.25E-06
6.25E-06
6.27E-06
6.27E-06
6.26E-06
6.25E-06
6.22E-06
6.19E-06
6.17E-06
6.15E-06
6.15E-06
6.16E-06
6.18E-06
6.20E-06
6.20E-06
6.20E-06
6.19E-06
6.16E-06
6.13E-06
6.12E-06
6.12E-06
6.10E-06
6.08E-06
6.06E-06
6.06E-06
6.08E-06
6.12E-06
6.19E-06
6.24E-06
6.26E-06
6.26E-06
6.25E-06
6.22E-06
6.22E-06
6.22E-06
6.23E-06
6.25E-06
6.26E-06
6.27E-06
6.27E-06
6.27E-06
6.30E-06
6.34E-06
6.37E-06
6.39E-06
6.41E-06
6.41E-06
6.39E-06
6.37E-06
6.37E-06
6.38E-06
6.39E-06
6.38E-06
6.35E-06
6.33E-06
6.33E-06
6.33E-06
6.36E-06
6.39E-06
6.40E-06
6.40E-06
6.37E-06
6.34E-06
6.30E-06
6.27E-06
6.25E-06
6.25E-06
6.25E-06
6.25E-06
6.22E-06
6.20E-06
6.18E-06
6.19E-06
6.22E-06
6.26E-06
6.26E-06
6.24E-06
6.21E-06
6.18E-06
6.16E-06
6.17E-06
6.20E-06
6.24E-06
6.28E-06
6.32E-06
6.34E-06
6.34E-06
6.35E-06
6.36E-06
6.41E-06
6.46E-06
6.51E-06
6.53E-06
6.52E-06
6.49E-06
6.47E-06
6.48E-06
6.51E-06
6.56E-06
6.60E-06
6.60E-06
6.58E-06
6.53E-06
6.47E-06
6.42E-06
6.41E-06
6.42E-06
6.42E-06
6.39E-06
6.35E-06
6.29E-06
6.22E-06
6.16E-06
6.12E-06
6.11E-06
6.12E-06
6.13E-06
6.13E-06
6.12E-06
6.11E-06
6.11E-06
6.12E-06
6.15E-06
6.22E-06
6.30E-06
6.35E-06
6.36E-06
6.34E-06
6.33E-06
6.35E-06
6.38E-06
6.44E-06
6.49E-06
6.53E-06
6.54E-06
6.54E-06
6.52E-06
6.49E-06
6.47E-06
6.46E-06
6.45E-06
6.43E-06
6.41E-06
6.38E-06
6.35E-06
6.34E-06
6.36E-06
6.40E-06
6.44E-06
6.46E-06
6.46E-06
6.47E-06
6.48E-06
6.49E-06
6.50E-06
6.51E-06
6.53E-06
6.54E-06
6.53E-06
6.52E-06
6.52E-06
6.55E-06
6.60E-06
6.63E-06
6.66E-06
6.68E-06
6.70E-06
6.71E-06
6.71E-06
6.70E-06
6.69E-06
6.67E-06
6.64E-06
6.62E-06
6.62E-06
6.63E-06
6.65E-06
6.69E-06
6.73E-06
6.77E-06
6.80E-06
6.82E-06
6.82E-06
6.81E-06
6.81E-06
6.82E-06
6.81E-06
6.80E-06
6.79E-06
6.77E-06
6.77E-06
6.77E-06
6.76E-06
6.77E-06
6.76E-06
6.76E-06
6.75E-06
6.74E-06
6.73E-06
6.71E-06
6.68E-06
6.65E-06
6.64E-06
6.64E-06
6.62E-06
6.58E-06
6.51E-06
6.45E-06
6.40E-06
6.38E-06
6.38E-06
6.40E-06
6.42E-06
6.44E-06
6.46E-06
6.45E-06
6.44E-06
6.44E-06
6.43E-06
6.41E-06
6.40E-06
6.41E-06
6.42E-06
6.42E-06
6.41E-06
6.43E-06
6.46E-06
6.50E-06
6.53E-06
6.55E-06
6.54E-06
6.53E-06
6.53E-06
6.52E-06
6.51E-06
6.50E-06
6.48E-06
6.47E-06
6.47E-06
6.48E-06
6.48E-06
6.48E-06
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Best Answer
    

    

								

								
Your data is sampled with Fs=10 Hz, Your Frequency spectrum is :
 Fs=10;
 N=length(x);
 fx=fft(x)/N;
 f=(0:N-1)*Fs/N;
 figure, plot(f(1:end/2),10*log10(abs(fx(1:end/2))))
						    
						
		
    
        

    

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Look at this example. A has 3 elements,
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>> B = [4 5] 
B =
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now concatenate them horizontally (side by side)
>> C = [A B] 
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Dimensions of matrices being concatenated are not consistent.
Why? Because, A has 3 elements wherein B has only 2. This is what is meant by "Dimensions are not consistent. Now let's say B also has 3 elements...
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Answer 1

Your data is sampled with Fs=10 Hz, Your Frequency spectrum is :

 Fs=10;
 N=length(x);
 fx=fft(x)/N;
 f=(0:N-1)*Fs/N;
 figure, plot(f(1:end/2),10*log10(abs(fx(1:end/2))))