Fast Fourier Transform (FFT) in a certain range of signal

Question

Jimmy 2015-8-22

0
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https://ww2.mathworks.cn/matlabcentral/answers/235193-fast-fourier-transform-fft-in-a-certain-range-of-signal

回答： Star Strider 2015-8-22

TestSig.mat

Greetings, I have a signal which consist of one 1000000x1 array (data) and one 1000000x1 array (time) which has been 'cut' and looks like the figure below.

Is it possible for me to do Fast Fourier Transform(FFT) on that signal? If possible, how do I perform the FFT on this signal? Assuming the operating frequency is 1000Hz

The coding that I have done to cut the signal are a follows:

 load('TestSig.mat');
[data_max,max_idx] = max(data);     %Locating the maximum data value
 time_at_max = time(max_idx);        %Locating time at the maximum data value
 left2  = data(max_idx-[120000:-1:1]);       %Taking few samples at the left from the max value
 right2 = data(max_idx+[1:200000]);          %Taking few samples at the right from the max value
 left2_time = time(max_idx-[120000:-1:1])    %Time of samples at the left from the max value
 right2_time = time(max_idx+[1:200000])      %Time of samples at the left from the max value
win_idx = (max_idx-120000):(max_idx+200000);
plot(time(win_idx), data(win_idx))