MATLAB: How to plot the fft of a pressure data

.csv filedatafftplotpressure

Hello. I have a question to all. I really want to know to plot fft my pressure data. So, I tried to do FFT, but it didn`t go well. If there is someone can catch mistake, then please may I get some advise? I attached my file!
 [fname,pathname] = uigetfile('.csv','Select CSV File to Load, Plot, Compute RMS & FFT');
    disp([pathname fname])
    data = csvread([pathname fname]);
    [N,m] = size(data);
    t = data(:,1);         %time in seconds
    x = data(:,2);         %array of data
    Fs = 1/(t(2)-t(1));
    figure(1)
    plot(t,x)
    xlabel('Time (s)');
    ylabel('Pressure');
    title(chamber pressure);
    grid on;
    freq = 0:Fs/length(x):Fs/2;           %frequency array for FFT
    xdft = fft(x);                        %Compute FFT
    xdft = 1/length(x).*xdft;             %Normalize
    xdft(2:end-1) = 2*xdft(2:end-1); 
    figure(3)
    plot(freq,abs(xdft(1:floor(N/2)+1)))
    xlabel('Frequency (Hz)');
    ylabel('Fourier spectrum');
    title(['FFT' chamber pressure]);
    grid on;

Best Answer

I continue to recommend the R2015a documentation for fft (link). Specifically not the code between the first (top) two plot figures.
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