Modify function_handle in Simulink matlab function

Hi there,

I want to modfy the type of function_handle in Simulink Matlab function. Here is the codes

nonConOption = 1;
nonlcon = [];
A = [];
b = [];
Aeq = [];
beq = []; 
x0 = [1/4,1/4];  
fun = @(x)100*(x(2)-x(1)^2)^2 + (1-x(1))^2;  
lb = [0,0.2];
ub = [0.5,0.8];  
if nonConOption ==  1
    nonlcon =  @circlecon;
end
x = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,nonlcon)   

function [c,ceq] = circlecon(x)
c = (x(1)-1/3)^2 + (x(2)-1/3)^2 - (1/3)^2;
ceq = [];
end

But the error reports

It is not possible to write a value of type function_handle to a variable of type double. Code generation does not support changing the type by assignment. To investigate the cause of the type mismatch, check the previous assignment or input type setting.

How to create an empty function_handle?

I don't want to repeat the call fmincon like

if nonConOption ==  1
    x = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,@circlecon)  
else
    x = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,[])  
end

best regards,

Tianyuan

[tianyuan wang]

When I try to use

nonlcon = @(x)[];

if nonConOption ==  1
    nonlcon =  @circlecon;
end

I reports:

It is not possible to write a value of type function_handle to a variable of type function_handle. Code generation does not support changing the type by assignment. To investigate the cause of the type mismatch, check the previous assignment or input type setting.

Answer 1

[Paul]

Assuming the ultimate goal is to have nonConOption as an input to the MatlabFunction block, I got this to work in the MatlabFunction block

function x = fcn(nonConOption)

%nonConOption = 1;
%nonlcon = [];
A = [];
b = [];
Aeq = [];
beq = []; 
x0 = [1/4,1/4];  
fun = @(x)100*(x(2)-x(1)^2)^2 + (1-x(1))^2;  
lb = [0,0.2];
ub = [0.5,0.8];
%{
if nonConOption ==  1
    nonlcon =  @circlecon;
else
    nonlcon = @(x) deal([],[]);
end

x = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,nonlcon,optimoptions('fmincon','Algorithm','sqp'));
%}
x = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,@(x) foofcn(x,nonConOption),optimoptions('fmincon','Algorithm','sqp'));
end

function [c,ceq] = foofcn(x,nonConOption)

if nonConOption == 1
    [c,ceq] = circlecon(x);
else
    c = [];
    ceq = [];
end


end

function [c,ceq] = circlecon(x)
c = (x(1)-1/3)^2 + (x(2)-1/3)^2 - (1/3)^2;
ceq = [];
end

The commented code worked fine for the case as posted where nonConOption = 1 is hard-coded, but it doesn't build if nonConOption is an input to the function.

I'm actually pleasantly surprised that this code is operable. I'm kind of curious about how the code for foofcn is generated where c is not empty on return from circlecon but is empty otherwise.

[tianyuan wang]

Hi @Paul

Thank you for your suggestions.

I changed the codes to

function x = fcn(nonConOption)
A = [];
b = [];
Aeq = [];
beq = []; 
x0 = [1/4,1/4];  
fun = @(x)100*(x(2)-x(1)^2)^2 + (1-x(1))^2;  
lb = [0,0.2];
ub = [0.5,0.8];
x = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,@(x) circlecon(x,nonConOption),optimoptions('fmincon','Algorithm','sqp'));
end

function [c,ceq] = circlecon(x,nonConOption)
c = [];
ceq = [];
if nonConOption == 1
c = (x(1)-1/3)^2 + (x(2)-1/3)^2 - (1/3)^2;
end
end

It also works well.

Answer 2

[Walter Roberson]

if nonConOption == 1
    nonlcon = @circlecon;
else
    nonlcon = @(varargin) deal([],[]);
end

[tianyuan wang]

Thank you @Walter Roberson for your suggestions.

Actually in @circlecon, it contains a complex if function. So I use the strategy posted above.

Best reagrds,

Tianyuan