evaluate

Evaluate optimization expression

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Syntax

val = evaluate(expr,pt)

Description

Use evaluate to find the numeric value of an optimization expression at a point.

Tip

For the full workflow, see Problem-Based Optimization Workflow or Problem-Based Workflow for Solving Equations.

example

val = evaluate(expr,pt) returns the value of the optimization expression expr at the value pt.

Examples

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Evaluate Optimization Expression At Point

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Create an optimization expression in two variables.

x = optimvar('x',3,2);
y = optimvar('y',1,2);
expr = sum(x,1) - 2*y;

Evaluate the expression at a point.

xmat = [3,-1;
    0,1;
    2,6];
sol.x = xmat;
sol.y = [4,-3];
val = evaluate(expr,sol)

val = 1×2

    -3    12

Evaluate Objective Function At Solution

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Solve a linear programming problem.

x = optimvar('x');
y = optimvar('y');
prob = optimproblem;
prob.Objective = -x -y/3;
prob.Constraints.cons1 = x + y <= 2;
prob.Constraints.cons2 = x + y/4 <= 1;
prob.Constraints.cons3 = x - y <= 2;
prob.Constraints.cons4 = x/4 + y >= -1;
prob.Constraints.cons5 = x + y >= 1;
prob.Constraints.cons6 = -x + y <= 2;

sol = solve(prob)

Solving problem using linprog.

Optimal solution found.

sol = struct with fields:
    x: 0.6667
    y: 1.3333

Find the value of the objective function at the solution.

val = evaluate(prob.Objective,sol)

val = -1.1111

Input Arguments

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`expr` — Optimization expression
`OptimizationExpression` object

Optimization expression, specified as an OptimizationExpression object.

Example: expr = 5*x+3, where x is an OptimizationVariable

`pt` — Values of variables in expression
structure

Values of variables in expression, specified as a structure. The structure pt has the following requirements:

All variables in expr match field names in pt.
The values of the matching field names are numeric.

For example, pt can be the solution to an optimization problem, as returned by solve.

Example: pt.x = 3, pt.y = -5

Data Types: struct

Output Arguments

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`val` — Numeric value of expression
double

Numeric value of expression, returned as a double.

Warning

The problem-based approach does not support complex values in an objective function, nonlinear equalities, or nonlinear inequalities. If a function calculation has a complex value, even as an intermediate value, the final result can be incorrect.