Creating Low Pass Filter for Time vs. Volts

I have a data set of time vs. volt obtained using an ossiliscope.

This data was imported to matlab and columns were extracted and the signal was plotted:

raw_time = raw_data(:,1);

voltage = raw_data(:,2);

plot(raw_time,voltage)

It then had to be normalized:

newtimeraw = ((raw_time - min(raw_time))/(max(raw_time)-min(raw_time)))*6;

The normalized signal was plotted:

plot(newtimeraw,voltage)

I am trying to create a low pass filter for the normalized signal and then apply a fourier transform. This is the code I have but I am genuinely lost, and am almost positive most of this code is incorrect in one way or another.

syms a b

fc = 1

fs = length(newtimeraw)/(max(newtimeraw)-min(newtimeraw))

signal = [newtimeraw,voltage]

[b,a] = butter(2,(fc/(fs/2)), 'low')

filtered_signal = filter(b,a,signal)

figure

freqz(b,a)

figure

subplot(2,1,1)

plot(newtimeraw,voltage)

subplot(2,1,2)

plot(newtimeraw,filtered_signal)

F_sig = 2*abs(fft(raw_data))/length(raw_data);

F_Fsig = 2 *abs(fft(filtered_signal))/length(filtered_signal);

freqVector = linspace(0, fs/2, length(filtered_signal/2+1));

figure

semilogx(freqVector,F_Fsig(1:end/2)+1)

[Star Strider]

Two observations:

1) Do not use the Symbolic Math Toolbox for this!

2) a second-order Butterworth lowpass filter is not going to do much to filter your signal.

[Navya Seelam]

Why are you trying to filter time i.e newtimeraw in the line 6 ? Aren't you trying to filter the voltage?