Calculate FFT from windowed time-based signal

Question

I have a time-based signal (Raw signal) sampled at 6 MHz and need to analyze it in freq. domain. I'm learning DSP and this is very first time I work with DSP. Could you please help to check if this code is correct or not. And I have couple of questions needed to be clarify:

1. I've heard about linear scale and logarithm scale in order to observe the amplitude easier. Could you please explain to me, in this case, how can I get the logarithm scale?

2. for some function in Matlab (for example fft, spectrogram, etc), how can I get the code (just in case I want to change something to adapt my need)?

input=V5k_a100; 
N=2048; L=4096; Fs=6e6; 
spectrumTemp=[];
for index=1:length(input)/L 
 slice = input(1+(index-1)*L:index*L); 
 abcd = hann(L) .* slice; 
 NFFT = 2^nextpow2(N); 
 spectrumTemp(index, :) = fft(abcd, NFFT)/L; 
end
f = [0:NFFT-1]*Fs/NFFT; 
freq = f(1:length(f)/2); 
time = [0:length(input)/L-1]*L/Fs; 
spectrum = spectrumTemp(:, 1:length(f)/2); 
mesh(time,freq',abs(spectrum'));

• Dennis Jaheruddin: If you want verification that the code is correct more information will be required. In particular encountered problems.

Answer 1

1. The easy way to plot something with a logarithmic scale would be to just take the logarithm of the variable.

   logspectrum = log(spectrum);

2. The source of some files is available when you type edit function name, example:

   edit unique

However, not all Matlab source is available, so unfortunately you cannot customize everything this easily.