My equation in for loop with 180 iterations is only giving me one answer

I am using matlab online so can not attach file, here is my code.

Though a is a 1x180 vector my t only has one output. How do I fix this?

My graph is giving me a horizontal line at 0.9152

anglei=90;
a=linspace(0,180,180);
T=zeros(numel(a));
for n=1:numel(a)
    t=((tan(anglei)-tan(a))/(tan(anglei)+tan(a)));
    T(:,n)=t;
    
end 
plot(T,a)
axis([0 180 0 1])

Answer 1

[madhan ravi]

You don't need a loop:

anglei=90;
a=linspace(0,180,180);
t=(tan(anglei)-tan(a))./(tan(anglei)+tan(a));
plot(t,a)

[Sarah Brianne]

Thank you so much! My graph does not look at all how I expected as I am trying to plot reflection as a function of angle of reflection using Fresnel's equations and it should max out at critical angle of 29.81 with a value of -1 but it is like -25 and follows no pattern I can understand, ,>.<,

[madhan ravi]

According to the code that you posted , this is the graph obtained I have no idea what Fresnel's equation is , accepting an answer means that the question has been solved. Are you sure about the formula ?

https://en.wikipedia.org/wiki/Fresnel_equations - the arguments of tan are added and subtracted whereas you subtract and add the tan functions.

[Sarah Brianne]

You solved my question in matlab, so I accepted your question. Mathematically it is blowing my mind right now cause I am trying to use it as justification for an angle in a medical device and the results are unexpected. Thank you nonetheless.

[Sarah Brianne]

It should look like the red line there and it is the same equation

[Stephen23]

@Sarah Brianne: read the tan documentation, the very first line clearly states "Tangent of argument in radians". Are the angles in your code radians? (hint: degrees). I would not expect to get particularly sensible outputs until you use the correct units.

This is why you should read the documentation for every function and operator that you use, no matter how trivial you think it is.

[Sarah Brianne]

@Stephen Cobeldick Thank you Stephen. I did try originally in radians and it still does not look right. I try a lot of different things just post the last thing I tried. I also tried with tand

Answer 2

[madhan ravi]

If you insist loop then:

anglei=90;
a=linspace(0,180,180);
T=zeros(size(a)); % look here
for n=1:numel(a)
    t=((tan(anglei)-tan(a(n)))/(tan(anglei)+tan(a(n))));
    %                    ^^^---------------------^^^---- missed it
    T(:,n)=t;  
end 
plot(T,a) 
% Don't limit the axis let matlab interpret with the limits!