While using Fmincon and obtaining unknown values is it possible to apply equality constraints for only 3rd and 4th element of the array and not the whole array containing 5 elements?

is it possible to minimize this fuction with the following constraints

Function : X(1)^1+X(2)^0.5+X(3)^4+X(4)^0.12+X(5)^-1

Constraints : X(3)=0 , X(4)=0 , X(2)<3

[Matt J]

If those are your only constraints, then the problem is unbounded. I can push the function to -Inf just by setting X=[-Inf,0,0,0,1]

Answer 1

[Walter Roberson]

Use the lb and ub constraints. Set lb equal to ub equal to 0 for positions 3 and 4. Set ub location 2 to 3*(1-eps). Set all other lb to -inf and all other ub to +inf

[Mukuntheshwaran Venkatesan]

what is 1-eps means?

[Walter Roberson]

eps is the smallest number such that 1-eps is different from 1 in floating point, the nearest you can get to 1 without being 1. When you multiply it by 3 you get the number that is the closest you can get to 3 without being 3 (or possibly the second closest, I would have to analyze further). The largest representable number that is less than 3.

Using this is necessary because the bounds are not lb < x < ub and are instead lb <= x <= ub. You cannot easily directly represent < 3 but you can express <= the closest number to 3.