How to calculate all the numbers in an array with some conditions?

I calculated some radian value of angles from the previouse code.

n = 8;
wl = 1;
d = wl./2;
AF = zeros(1,50);
th= 20;

angle_rad = th*pi./180;

phi= (2.*pi.*d .*sin(angle_rad))./wl;

and usd a for loop to display all the numbers of phi

for a = 1:n
  AF = (a-1).*phi
end

The problem is I need the value of phi is restricted between-2pi and 2pi. (The angle value (th) I stated was 20 degree but it can be changed, such as -50 degree)

I tried the if elseif statement

for a = 1:n
  AF = (a-1).*phi
      if   AF >= 2.*pi
           AF = AF - 2.*pi;
       
    
      elseif AF <= -2.*pi
             AF = AF + 2.*pi;    
          
end
end

It's not working and I am not sure what to do with it, hope to get help from you guys！ Thanks!

Answer 1

[KALYAN ACHARJYA]

"The problem is I need the value of phi is restricted between-2pi and 2pi. (The angle value (th) I stated was 20 degree but it can be changed, such as -50 degree)"

Case 1: Any value you enter, which is restricted phi within -2pi to + 2pi.

n=8;
wl=1;
d=wl/2;
th=.....%Enter any Value
angle_rad=th*pi/180;
phi=2*pi*d*sin(angle_rad)/wl

Case 2: Or you can limiting such data limiting case using while loop

n=8;
wl=1;
d=wl/2;
while true
th=input('\nPlease Enter the th: ');
angle_rad=th*pi/180;
phi=2*pi*d*sin(angle_rad)/wl;
if phi>=-2*pi && phi<=2*pi
    break
else 
disp('#Wrong data Input for th')
th=input('\n Re-Enter the th: ');   
end 
end 

Case 3: you can nulify such data, if the condition is fail

[ZIYI WENG]

Thanks for your help!

I am sorry that I did not state my question clealy. The problem is whatever the entering theta is , I will get n values of phi and they stay in the array AF.

for a = 1:n
  AF = (a-1).*phi
end

However, since I am calculating angle(phi are angles) The value of phi will be larger than 2pi or smaller than -2pi. That depends on the theta. At the same time, I cannot just abandon the values of phi which out of the range(-2pi to 2pi). I need to change them and control them by keep minus 2pi when the value is over than 2pi until it is smaller or equal to 2pi. On the opposite side, if the value is smaller than -2pi, I need to keep plus 2pi until the value is larger or equals to -2pi.

[ZIYI WENG]

I solved it, thanks anyway!