Hi$,$ I found this code on Chegg from the expert, and I never used the polar function, so could you please provide the "comments"$`$ on the code line below so I can understand it$?$ Thank you!

$``$

clear

close all

clc

h $=$ fir$1(10,0\mathrm{.}3)$; $\%$FIR filter

figure; frevalz$01($h$,1)$;

$\%4$

$[$b$1,$ a$1]=$butter$(10,0\mathrm{.}3)$;$\%$IIR filter

figure; frevalz$01($b$1,$a$1)$;

$\%5$

N$=20$;

n$=0$:$1$:N$-1$;

$```$

$```$

$\%$Fir filtering

y$1=$filter$($h$,1,$x$)$;

$\%$IIR filtering

y$2=$filter$($b$1,$a$1,$x$)$;

figure;

subplot$(211)$

stem$($n$,$y$1)$;grid;xlabel$(\text{'}$n$\text{'})$;ylabel$(\text{'}$y$($n$)\text{'})$;title$(\text{'}$Output of FIR filter'$)$

subplot$(212)$

stem$($n$,$y$2)$;grid;xlabel$(\text{'}$n$\text{'})$;ylabel$(\text{'}$y$($n$)\text{'})$;title$(\text{'}$Output of IIR filter'$)$

Function script

function $[$P$]=$ frevalz$01($b$,$a$,$Ts$)$

$\%$To get pole zero plot

P $=[$zeros$($length$($b$)-1,1)$;roots$($a$)]$;

NP $=$ length$($P$)$;

z $=[$zeros$($length$($a$)-1,1)$;roots$($b$)]$;

NZ $=$ length$($z$)$;

while P$(1)==$ Z$(1)$

P $=$ P$(2$:NP$)$;

Z $=$ Z$(2$:NZ$)$;

NP $=$ length$($P$)$;

NZ $=$ length$($Z$)$;

end

if$($nargin$==2),$Ts$=1$;end

clf; N $=1024$;

Rep $=$ real$($P$)$;Imp $=$ imag$($P$)$;

Rez $=$ real$($Z$)$;Imz $=$ imag$($Z$)$;

Ap $=$ abs$($P$)$;Pp $=$ angle$($P$)$;

Az $=$ abs$($Z$)$;PZ $=$ angle$($Z$)$;

maxz $=$ max$([$AZ$\text{'}$ Ap$\text{'}1\mathrm{.}1])$;

if$(($NP$==0)$ & $($NZ $=0))$

polar$($ Pz$,$ Az$,\text{'}$ro$\text{'})$;hold on;

elseif$(($NZ$==0)$ & $($NP~$=0))$

polar$($ Pp$,$ Ap$,\text{'}$mx$\text{'})$;hold on;

else

if max$($AZ$)>$max$($Ap$)$

polar$($ PZ$,$ AZ$,\text{'}$bo$\text{'})$;hold on;

polar$($ Pp$,$ Ap$,\text{'}$mx$\text{'})$

polar$($ Pp$,$ Ap$,\text{'}$bx$\text{'})$;hold on;

polar$($ Pz$,$ Az$,\text{'}$mo$\text{'})$

end

end

$[$H$1,$ w$]=$ freqz$($b$,$a$,$N$,$'whole'$)$;

Amp $=$ abs$($H$1)\text{'}$;

Pha $=$ angle$($H$1)\text{'}$;

w $=$ w$\text{'}$;

Amp $=[$ Amp$($N$/2+1$:N $)$ Amp$(1$:N$/2)]$;

w $=[-$w$($ N$/2+1$:$-1$:$2)$ w$(1$:N$/2)]$;

Pha $=[$ Pha$($ N$/2+1$:N $)$ Pha$(1$:N$/2)]$;

w $=-1$:$2/($length$($w$)-1)$:$1$;

w $=$ w$/2$;

subplot$(221)$

maxz $=$ max$([$Az$\text{'}$ Ap$\text{'}1\mathrm{.}1])$;

if$(($NP$==0)$ & $($NZ $=0))$

polar$($ PZ$,$ Az$,\text{'}$mo$\text{'})$;hold on;

elseif$(($NZ$==0)$ & $($NP~$=0))$

polar$($ Pp$,$ Ap$,\text{'}$bx$\text{'})$;hold on;

else

if max$($Az$)>$max$($Ap$)$

polar$($ PZ$,$ Az$,\text{'}$mo$\text{'})$;hold on;

polar$($ Pp$,$ Ap$,\text{'}$bx$\text{'})$

else

polar$($ Pp$,$ Ap$,\text{'}$bx$\text{'})$;hold on;

polar$($ PZ$,$ Az$,\text{'}$mo$\text{'})$

end

end

grid

c $=-$pi:$2*$pi$/200$:pi;

polar$($c$,$ ones$(1,$length$($c$)),\text{'}$r$\text{'})$;

title$(\text{'}$Pole$-$Zero Plot of Filter'$)$

axis$([-$maxz,maxz, $-$maxz, maxz$])$

hold off;

$\%$Impulse response

h$=$filter$($b$,$a$,[1$ zeros$(1,49)])$;

subplot$(222)$

stem$(0$:Ts:$49*$Ts$,$h$,\text{'}$r$\text{'})$;

title$(\text{'}$Impulse Response'$)$;grid;xlabel$(\text{'}$n$\text{'})$;ylabel$(\text{'}$h$($n$)\text{'})$

$\%$Magnitude and phase responses

for k$=1$:N

if $($Amp$($k$)==0)$ M$($k$)=-60$;

else, M$($k$)=2*10*$ log$10($Amp$($k$))$; end

end

subplot$(223),$ plot$($w$,$ M$,\text{'}$b$\text{'})$

title$(\text{'}$Magnitude Response'$)$;grid;

xlabel$(\text{'}$Normalized Frequency $\text{'})$

ylabel$(\text{'}|$H$|$ in dB$\text{'})$

subplot$(224),$ plot$($w$,$ Pha,$\text{'}$g$\text{'})$

title$(\text{'}$Phase Response'$)$;grid;

xlabel$(\text{'}$Normalized Frequency $\text{'})$

ylabel$(\text{'}\text{'})$

end

$```$