how can I preallocate for speed in a loop?

Hello,

This is my current code I keep getting an error about pre-allocating my x_p variable.

Would anyone know who I could fix it?

Thank you.

% bisection method

bisection = bisec(depth,x_l,x_u,10,.01);

function ANS = bisec( f, x_l, x_u, itera, error )

%BISEC bisection method

for i = 1:itera

x_p(i) = (x_l + x_u)/2;

if ((f(x_l)*f(x_p(i))) < 0)

x_u = x_p(i);

elseif ((f(x_l)*f(x_p(i))) > 0)

x_l = x_p(i);

elseif ((f(x_l)*f(x_p(i))) == 0)

break;

end

if ((i>1) && (abs((x_p(i)-x_p(i-1))/x_p(i)) * 100) < error)

break;

end

end

ANS = x_p(end);

end

Answer 1

[StefBu]

Hi. Since x_p grows in each iteration of your for-loop you can easily define its size at the begining.

Just use this before your loop:

x_p = zeros(itera,1);

Greetings

Stefan