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From: kay on 15 Apr 2010 11:39
im using fmincon toolbox GUI to find the minimum value of width to be designed.
here is the function file:

function f = Design_area(x,sigma)
f = x(1)*x(2);

function[c,ceq] = beam_constraint(x,sigma)
sigma = 200*10^8;
c(1) = 1000 - (sigma*x(1)*x(2));
c(2) = 1000 - (sigma*x(1)*x(2));
ceq = [];
lb = [10 0];
ub = [20,inf];

where my constraints are
1) 1000/x(1)*x(2)* <= sigma
2) 10<=x(1)<=20
3)10<=x(2)<=20


i want my initial dimension to be x(1)=20 and x(2)=20..how do i write it?
for the start point, i entered [20 1]. is it correct?
From: kay on 15 Apr 2010 12:00
some more information for my problem:
width=x(1)
height=x(2)

as u can see in the code, i wrote the upper n lower boundary :
lb = [10 0];
ub = [20,inf];

but then how do the function knows it is for which variable? i mean, i have 2 variables x(1) and x(2) but..how do i write the boundary for both of my variables?
anyway, is the code for boundary that i wrote is correct?

one more thing, when i change my start point to [20 1], this is the output:

Max Line search Directional First-order
Iter F-count f(x) constraint steplength derivative optimality
0 3 20 0
1 6 0.049751 -0.002494 1 -19.9 0.995
2 9 1.53649e-007 -7.702e-009 1 -0.0498 8.29e-006
3 12 5e-008 -2.506e-009 1 -1.04e-007 1.52e-017

Optimization terminated: first-order optimality measure less
than options.TolFun and maximum constraint violation is less
than options.TolCon.
Active inequalities (to within options.TolCon = 1e-006):
lower upper ineqlin ineqnonlin
2 1


-->the final value from the optimtool gives me value of x(1)=19.95 and x(2)=0 and objective function value = 5.00000e-8 (iteration 3)
how do interpret the output? i dont understand.please help ..
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