Fast Fourier Transform for csv file with multiple column

Hello,

I have a set of .csv files containing about 20,000 lines each. The first column is a time interval (10ms) and the second, third and forth columns are for X, Y, and Z axes data respectively.

After reading this set of data and plotting them in their time domain, I am trying to perform a Fast Fourier Transform for them and plotting them in a graph, and also to generate a new .csv file with the data that underwent fft.

I've been reading up some other post of fft but seems like that are some parameters such as frequency that I am unsure of how I can get them.

I'm not sure how I should go about solving this and hope that some of you may be able to help me with this issue.

I have attached my code below

{
folderSource= 'C:\Users\r-o-n\Desktop\DP2\Testing2\csvtest\Incoming';

folderDestination= 'C:\Users\r-o-n\Desktop\DP2\Testing2\csvtest\Incoming\';
csvFiles=dir(fullfile(folderSource,'*.csv'));

for k=1:length(csvFiles)
  baseFileName=csvFiles(k).name;
  fullFileName=fullfile(folderSource,baseFileName);
  inData=csvread(fullFileName,1,0);
end

t=inData(:,1);
x=inData(:,2);
y=inData(:,3);
z=inData(:,4);

subplot(3,1,1);
plot(t,x,':');
title('X-Axis');
ylabel('X-Acceleration (mg)');

subplot(3,1,2);
plot(t,y,':');
title('Y-Axis');
ylabel('Y-Acceleration (mg)');

subplot(3,1,3);
plot(t,z,':');
title('Z-Axis');
ylabel('Z-Acceleration (mg)');
xlabel('Time (ms)');
%would like to perform FTT to the data (both X,Y and Z) 
xdft = fft(inData(:,2));

}

Thanks in advance! :)

Best Regards, Ron

Answer 1

[Dimitris Kalogiros]

You must find Fsampling.

You can achieve this by observing values of vector t. If t(k)-t(k-1) is the same for each 1<k<length(t) then you have "uniform sampling" and everything is OK for you. You can use as Fsampling the quantity 1/(t(k)-t(k-1)) , for whatever k you want, and follow the recipes of the "other posts"

Good luck