whats this line do?

y=[zeros(10,20000),x,zeros(10,20000)];
y2=abs(fftshift(fft(real(y(2,:)))))/length(y);

thanks!!!

Answer 1

[Sean de Wolski]

• It defines y as x padded with 20000 columns on both sides
• It takes the DFT of the real part of the second row of y, shifts it to 0 takes the absolute value and divides by the length of the row.

Answer 2

[itsik]

ok so what this is do? where is the fft take a place? lets say x=[10 X 1000]

y=[zeros(10,20000),x,zeros(10,20000)];
y2=abs(fftshift(fft(real(y(2,:)))))/length(y);
y3=abs(fftshift(fft(real(y(3,:)))))/length(y);
y4=abs(fftshift(fft(real(y(4,:)))))/length(y);

i just cant understand that line : y=[zeros(10,20000),x,zeros(10,20000)];

thanks!

[Sean de Wolski]

It zero pads x with 10x20000 zeros on each side (columnwise)

try it on a small scale

x = magic(3);

y = [zeros(3,10),x,zeros(3,5)]