plots with if, elseif and else

c2=1800;
c1=1500;
for ai=0:0.01:pi/2;
    at=asin(sin(ai).*c2./c1);R=(c2./cos(at)-c1./cos(ai))./(c2./cos(at)+c1./cos(ai));
    if ai<ac
       phase=2.*atan(sqrt((cos(ac)./cos(ai)).^2-1));
       R=(c2./cos(at)-c2./cos(ai))./(c2./cos(at)+c1./cos(ai));
    elseif ai>=ac
       phase=0;
       R=1;
    end 
end 
figure
plot(ai,R);
hold on
plot(ai,phase);

when I run the codes, nothing appears in the plots. and when I check the values of R and phase, and find that R=1 and phase=0. anyone can help me correct the codes? thank you very much

[EDITED, Jan, please use a proper code formatting - thanks]

Answer 1

[Star Strider]

You didn’t supply a value for ‘ac’ so I made one up to be sure the code works.

Your code can (I believe) be reduced to a few lines:

ac = 2;                         % <= This Needs Your Definition!
c2=1800;
c1=1500;
ai=0:0.01:pi/2;

at=asin(sin(ai).*c2./c1);
R = @(ai) [((c2./cos(at)-c2./cos(ai))./(c2./cos(at)+c1./cos(ai))).*(ai<ac) + (1).*(ai>=ac)];
phase = @(ai) [(2.*atan(sqrt((cos(ac)./cos(ai)).^2-1))).*(ai<ac)];

figure(1)
plot(ai,R(ai));
hold on
plot(ai,phase(ai));
hold off

The anonymous functions for ‘R’ and ‘phase’ are simple vectors where the functions take the values you want to assign to them according to the logic tests you set for them.

The results are complex, so you will likely want to decide how to detail with that (plot imaginary parts separately for instance).

Does this do what you want?