How to find frequency contents in this signal below?

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Abhishek Nayak 2019-8-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/476896-how-to-find-frequency-contents-in-this-signal-below

编辑： Adam Danz 2019-8-26

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Adam Danz 2019-8-20

fft() ?

https://www.mathworks.com/help/matlab/ref/fft.html

Abhishek Nayak 2019-8-20

编辑：Abhishek Nayak 2019-8-20

在 MATLAB Online 中打开

Thanks for answering the question, but I was not able to get the adequate results by using fft. Can you please figure out the probem in the folowing code

The code I followed is shown below.

%% to obatin the datas in the figure
h = findobj(gca,'Type','line')
x=get(h,'Xdata') ;
y=get(h,'Ydata') ;
%% using fft to obtain the frequency contents in the signal
sam=x(end)/length(x); % sampling time
X=fft(y);             % using fft
P2=abs(X/length(X));  % To normalize and obtain magnitude
P1=P2(1:1+(length(X)+1)/2); % To compute the single-sided spectrum P1
fre=(1/sam)*(0:(length(X)+1)/2); % To obtain the spread of freqency
figure(25)
plot(fre,P1)    % To plot the frequency contents in the signal

It can be seen from the asked figure that the freqency contenets are in low freqency range but the obtained results are in very fast freqency range.

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Answer 1

Abhishek Nayak 2019-8-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/476896-how-to-find-frequency-contents-in-this-signal-below#answer_389086

编辑：Adam Danz 2019-8-26

在 MATLAB Online 中打开

I figured it out finaly,

there was a mistake in the code

%% to obatin the datas in the figure
h = findobj(gca,'Type','line')
x=get(h,'Xdata') ;
y=get(h,'Ydata') ;
%% using fft to obtain the frequency contents in the signal
sam=x(end)/length(x); % sampling time
X=fft(y);             % using fft
P2=abs(X/length(X));  % To normalize and obtain magnitude
P1=P2(1:1+(length(X)+1)/2); % To compute the single-sided spectrum P1
fre=(1/sam)*(0:(length(X)+1)/2)/length(X); % To obtain the spread of freqency
figure(25)
plot(fre,P1)    % To plot the frequency contents in the signal