Can you explain to me the last part of this code? Thanks in advance!

close all

clear all

%properties of rocks

Vs_soil=170;

Psoil=1.5;

Hs=70;

Vs_rock=1000;

Prock=2.4;

damp=0;

%impedance ratio

IC=((Prock*Vs_rock)/(Psoil*Vs_soil));

%Ground fundamental frequency

f0=Vs_soil/(4*Hs);

%Maximum magnification for one dimensional monolayer

A0=1/((1/IC)+0.5*pi*damp);

%harmonic frequencies

d=10;

dx=1/d;

n=-0.5:dx:8;

fn=(2*n+1)*f0;

%Magnification / Resonant frequency

% I didn't get this part of the code after "a=cos(w*Hs/Vs_soil)". Why are " round, isinf " used here?

w=2*pi*fn;

a=cos(w*Hs/Vs_soil);

y=roundn(a,-4);

Fw=1./abs(y);

Fw(isinf(Fw))=A0;

%Let's draw the magnification graph

plot(fn,Fw);

title('magnification graph');

xlabel('f(Hz)');

ylabel('Magnification F(w)');

legend('Transfer Function');

grid;

print -djpeg magnification graph

Answer 1

[Voss]

y=roundn(a,-4);

rounds a to the nearest multiple of 10^-4 and stores the result in y.

Fw(isinf(Fw))=A0;

replaces elements of Fw that are Inf or -Inf with A0.