Import Text Data and Plot FFT
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Hi, I'm very new to MatLab and don't know too much. I need to take a series of data from a text file and plot the Fourier Transform. The sample rate is 100samples/second or deltaT = 0.01. Thank you for your help.
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Image Analyst
el 16 de Oct. de 2016
Attach your text data file. Otherwise, try csvread(), dlmread(), importdata(), load(), textscan(), readtable(), or similar routines.
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Image Analyst
el 16 de Oct. de 2016
Here is some more complete code:
data = importdata('p1.txt')
spectrum = fft(data);
deltaT = 0.01;
numElements = length(spectrum)
indexOf0 = numElements / 2
shiftedSpectrum = fftshift(abs(spectrum));
f = (1 / deltaT) * linspace(-numElements/2, numElements/2, numElements);
plot(f, shiftedSpectrum, 'b.-', 'LineWidth', 2, 'MarkerSize', 16);
grid on;
title('Spectrum of Data', 'FontSize', fontSize);
xlabel('Frequency', 'FontSize', fontSize);
ylabel('Power', 'FontSize', fontSize);
% Make bolder y axis
line([indexOf0, indexOf0], ylim, 'Color', 'k', 'LineWidth', 3);
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
dang khoa tran
el 17 de Dic. de 2019
Hello, so do you have any idea to do inverse FFT using the text file?
Thank you
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dang khoa tran
el 18 de Dic. de 2019
Thank you for your reply. But then I do this, it still shows the same result as that when doing with "fft and fftshift"
My case is : There is a variation of electric filed amplitude along the propagation distance. And I want to transform this into the variation along the time domain so that I can get the "pulse duration". So do you have any idea?
Below is the attactment of the text file.
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