Hi Manik,
The issue seems to be in the implementation. The error Length of lower bounds is < length(x) is because the size of "x0" and vectors "lb" and "ub" are different during the subsequent iterations.
I've solved it using two methods as decribed below:
Method-1: Instead of increasing the size of vector "x0" during different iterations, it can be made constant by using "x0" as 2x2 matrix.
x0(1) =-4;
x0(2) =4;
and in the loop, the corresponding change can be made:
x0(1) = -4 + k * (1/18);
x0(2) = 4 + k * (1/36);
This works because now the size of vector "x0" remains constant and is same as size of vectors "lb" and "ub".
Method-2: Increasing the size of vectors "lb" and "ub" during different iterations. The aim is to make size of vectors "lb", "ub" same as "x0".
% Define bounds
lb(1,1) = -Inf;
lb(1,2) = -Inf;
ub(1,1) = -Inf;
ub(1,2) = Inf;
and in the loop, the corresponding change can be made:
lb(i,1) = -Inf;
lb(i,2) = -Inf;
ub(i,1) = Inf;
ub(i,2) = Inf;
This works because now the size of vectors "lb" and "ub" remains constant and is same as size of vector "x0".
For futher information, you can refer to documentation of fmincon function: https://in.mathworks.com/help/optim/ug/fmincon.html
Hope it helps!!
