Is the window function automatically used when doing the fft function, or do I have to enter code to use the window function?

I used the fft function to make frequency measurements from the data.

At this time, I would like to know what the window function is using.

When using only the fft function, please tell me what kind of window function is used or if the window function is not applied

t = 0:0.01:1;
data = sin(2*pi*t);
plot(t,data)

fftdata = abs(fft(data));
% At this time, is the window function automatically used?

f = (0:length(data)-1)*1/length(data);
plot(f,fftdata)

Answer 1

[Star Strider]

The fft defaults to a rectangular window that is the length of the signal. That is the only one that is ‘autoomatically’ used. Any others would have to be provided specifically as part of the fft call.

There are several window funcitons available in the Signal Processing Toolbox.

Adding a Hanning window (the hann function) to your code would work like this —

t = (0:0.01:1).';                                               % Transpose To Column Vector
data = sin(2*pi*t);
plot(t,data)

L = numel(data)

L = 101

fftdata = abs(fft(data.*hann(L)));                              % Use Hanning Window
% At this time, is the window function automatically used?

f = (0:length(data)-1)*1/length(data);
plot(f,fftdata)

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[正義 金田]

Thank you for teaching me carefully.

It was very helpful.

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

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