Error: "Not enough input arguments"

Hi. I'm new to matlab and I'm trying to optimize a distillation column with the NSGA II algorithm. However, I am having the following error: "Not enough input arguments". Can someone help me?

function [Obj, Cons] = Fun_Objective(X)
global Aspen

Stages = X(1) + 2;
Pressure = X(2);
Feed_Stage = round((Stages-4)*X(3) + 2);

Aspen.Tree.FindNode("\Data\Blocks\B2\Input\NSTAGE").Value = Stages;
Aspen.Tree.FindNode("\Data\Blocks\B2\Subobjects\Column Internals\INT-1\Input\CA_STAGE2\INT-1\CS-1").Value = Stages - 1;
Aspen.Tree.FindNode("\Data\Blocks\B2\Input\PRES1").Value = Pressure;
Aspen.Tree.FindNode("\Data\Blocks\B2\Input\FEED_STAGE\S50").Value = Feed_Stage;

    Aspen.Reinit; % Reinit simulation
    Aspen.Engine.Run2(1); %Run the simulation. (1) ---> Matlab isnt busy; (0) Matlab is Busy;
    time = 1;
    Error = 0;
    while Aspen.Engine.IsRunning == 1 % 1 --> If Aspen is running; 0 ---> If Aspen stop.
        pause(0.5);
        time = time+1;
        if time==600 % Control of simulation time.
            Aspen.Engine.Stop;
            Error = 1;
        end
    end
    
Conv = Aspen.Tree.FindNode("\Data\Results Summary\Run-Status\Output\PER_ERROR").Value; %Convergence Assessment
    if Error == 0 && Conv == 0
        Pur = Aspen.Tree.FindNode("\Data\Streams\S4\Output\MASSFLOW\MIXED\ACROL-01").Value/Aspen.Tree.FindNode("\Data\Streams\S4\Output\MASSFLMX\MIXED").Value;
        Purity = 0.95 - Pur; %This means: Pur > 0.95 mol frac.
        %Recovery > 0.98
        Recovery = 0.98 - (Aspen.Tree.FindNode("\Data\Streams\S4\Output\MASSFLOW\MIXED\ACROL-01").Value/Aspen.Tree.FindNode("\Data\Streams\S50\Output\MASSFLOW\MIXED\ACROL-01").Value);
        %Constraints Vector
        c(1,1) = Purity;
        c(1,2) = Recovery;
        Cons = (c>0).*c; %Only accept unsatisfied constrainst: c > 0
        CAPEX = AcrilonitrilaCAPEX()/10; %Fixed Distillation Cost
        OPEX = AcrilonitrilaOPEX(); %Operating Distillation Cost
        Obj  = [CAPEX, OPEX]; %Objectives Function. CAPEX vs OPEX
    else
        Obj  = [2e7, 2e7]; 
        Cons = [1, 1];
    end
end

[Walter Roberson]

Where is the error message being generated? What is the code you are using to run this code?

[Eduardo Braga]

Hi

Error in Fun_Objective (line 4)

Stages = X(1) + 2;

i am following this code:

https://www.mathworks.com/matlabcentral/fileexchange/74745-aspen-plus-matlab-optimization-of-distillation-column?s_tid=FX_rc1_behav

Answer 1

[Walter Roberson]

You cannot run the objective function directly: you need to run a function such as the supplied Opt* function which sets up the conditions for everything to be called.

[Eduardo Braga]

I got it! thank you so much!