How to reconstruct original signal from fft?

Hello everyone!!

I have some measurement data (current) from oscilloscope in .csv file format. I need to make fft from that data and reconstruct original signal from dominant frequencies. I've done fft using code

clc;clear all;close all;

data = csvread('F0000CH2.CSV');

t=data(:,4);

x=data(:,5);

plot(t,x)

dft=fft(x);

plot(abs(dft));

How can I read current values for dominant frequencies and is it possible to reconstruct the original oscilloscope signal from only using dominant frequencies? Below is original current and voltage signal from oscilloscope. Thanks for your help. :)

Answer 1

[Walter Roberson]

After you fft(), you zero the entries with lower magnitudes (absolute value), and then you ifft() to reconstruct.

[Matej Pericic]

I have only one more question if you can help me. How can I read current values for dominant frequencies?

[Walter Roberson]

... they are the entries you didn't zero out?

If you want to know what frequencies they are, then I suggest you look at the examples in the fft documentation to see how they construct the frequency labels for the graphs.

[Matej Pericic]

Thank you for you time and answers. I will look at the examples.