How to terminate an if-elseif-else statement once a condition is met.

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I want a situation whereby if the first 'if' statement is true (norm_sn <= del), the code should calculate x_plus and exit the if condition (jump to calculate f_x), or if the 'if' statement is false and the 'elseif' statement is true (del <= norm_s_cp), the code should calculate x_plus and exit the if statements (jump to calculate f_x). if none of the first two is true, then it can calculate the 'else'. I want it to be in that order. Can someone help me out. Thank you.
function [x_plus,grad,norm_grad,f_x,f_xplus,m_xplus] = dogleg(f,x,del)
syms x_1 x_2 aux
grad = subs(gradient(f,[x_1,x_2]),[x_1,x_2],x');
norm_grad = norm(grad);
H = subs(hessian(f,[x_1,x_2]),[x_1,x_2],x');
%
s_n = -H^-1*grad; norm_sn = norm(s_n);
lambda_star1 = norm_grad^2/(grad'*H*grad);
s_cp = -lambda_star1*grad; norm_s_cp = norm(s_cp);
if norm_sn <= del
x_plus = x + s_n;
elseif del <= norm_s_cp
x_plus = x - (del/norm_grad)*grad;
else
gamma = norm_grad^4/((grad'*H*grad)*(grad'*abs(s_n)));
%gamma = norm_s_cp*norm(grad)/grad'*abs(s_n);
eta = 0.8*gamma + 0.2;
s_ncap = eta*s_n;
lambda = solve(norm(s_cp + aux*(s_ncap - s_cp))^2 == del^2);
x_plus = x + s_cp + lambda(lambda>0)*(s_ncap - s_cp);
end
f_x = subs(f,[x_1,x_2],x');
f_xplus = subs(f,[x_1,x_2],x_plus');
m_xplus = f_x + grad'*(x_plus - x) + 0.5*(x_plus - x)'*H*(x_plus - x);
end
  4 Comments
Rik
Rik on 11 Nov 2018
if...elseif...else...end is not a loop. If you want something to happen under some condition, make sure you have that as a test. See the example below for what happens when conditions overlap.
cond1=true;cond2=true;
if cond1 && cond2
disp(1)
elseif cond1
disp(2)
elseif cond2
disp(3)
else
disp(4)
end

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Accepted Answer

Image Analyst
Image Analyst on 12 Nov 2018
I don't see a loop but if there were, you could put a "break" statement there. As it is, you can put a "return" statement wherever you want to exit the function immediately, as long as all the output variables have been assigned.
  1 Comment
Gideon Idumah
Gideon Idumah on 14 Nov 2018
Thank you.
I just created a new function, and put a return at the end of the "if" and "elseif" statement.

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