how to use if in matlab for 2 matrix condition?

i have 2 reflection coefficient equations R1 and R2 from K with condition absolute must below 1, i use if command for this situation .But when i plot the graph the absolute reflection coefficient still above 1. (K is matrix with 1 column and 201 row)

R1=K+sqrt(K.^2-1);
R2=K-sqrt(K.^2-1);
     if abs(R1)<1
        r=R1;
     else
        r=R2; 
     end

Answer 1

[madhan ravi]

r=R2;
r(abs(R1)<1)=R1

[sukma aditya]

im sorry can you write the full code?

i cant understand hehe