Not enough input arguments. Help?

Not enough input arguments. Error in constraint (line 11) k1 = E*x(1)/l(1)*[(cos(a(1)))^2,sin(a(1))*cos(a(1));sin(a(1))*cos(a(1)),(sin(a(1))^2)];

This is my code:

function [c,ceq] = constraint(x)

% constraint: axial stress<=400N/m2

% x is the area of bar, x1=A1,x2=A2,x3=A3

% Load, geometry and materal

F = [10000e3;-2000e3];%unit change (kN--N)

E = 70E9;%Pa = N/m2

l = [2 2/sqrt(3) sqrt(2)];%m

a = [deg2rad(-30) deg2rad(-60) deg2rad(-135)];%rad

%bar 1 global matrix at node 4

k1 = E*x(1)/l(1)*[(cos(a(1)))^2,sin(a(1))*cos(a(1));sin(a(1))*cos(a(1)),(sin(a(1))^2)];

%bar 2 global matrix at node 4

k2 = E*x(2)/l(2)*[(cos(a(2)))^2,sin(a(2))*cos(a(2));sin(a(2))*cos(a(2)),(sin(a(2))^2)];

%bar 3 global matrix at node 4

k3 = E*x(3)/l(3)*[(cos(a(3)))^2,sin(a(3))*cos(a(3));sin(a(3))*cos(a(3)),(sin(a(3))^2)];

% nodal displacement in node 4

k = k1+k2+k3;

d4 = inv(k)*F; %P

%force component at each bar

f1 = k1*d4;

f2 = k2*d4;

f3 = k3*d4;

%axial force

s1 = (sqrt(f1(1)^2+f1(2)^2))/x(1);

s2 = (sqrt(f2(1)^2+f2(2)^2))/x(2);

S3 = (sqrt(f3(1)^2+f3(2)^2))/x(3);

%inequlity constraint

Fo = [s1 s2 S3]; %N/mm2

c = Fo-400;

%Equality constraint

ceq = []; %no equality constraint

end

[krishna kotha]

hi iam krishna

its showing error in

" x(1)/l(1)"

i removed this and excuted it. and it showing the results.

i dont know what you are doing but the error is in function the variable "x"

[Ankit]

it is working fine. how you are passing x (areas) to your function?

[c,ceq] = constraint([2 3 4])

Output in Matlab:

c =

   1.6326e+06   1.8391e+06   1.5596e+06


ceq =

     []

[darova]

Shouldn't your global matrix look liek this (color - local matrices)?

Answer 1

[Constantino Carlos Reyes-Aldasoro]

Your problem may be that you are calling your function without the required input parameters your function requires one parameter

function [c,ceq] = constraint(x)

so if you call your function without input parameters it will create an error. I created a simplified version of a function:

    function [c,ceq] = constraint(x); c=x;ceq=x;end

and then call it with/without parameters, look:

>>  [c,ceq] = constraint(2);
>> [c,ceq] = constraint();
Not enough input arguments.

Error in constraint (line 1)
function [c,ceq] = constraint(x); c=x;ceq=x;end
 
>> 

Hope this helps. If this does not solve your question, let me know. If it does, please accept the answer.

[Charlotte Massie]

Hi,

I am still unsure what you mean and how i can fix my code. Any further help would be appreciated.

[Constantino Carlos Reyes-Aldasoro]

The code (your function) is fine, the problem is when you call the function. Somewhere, outside the function you must be calling the function, and you have not placed the value of x in that call.

Correct

% here you do something
% then you define x
x = 2;
% then you call your function
[c,ceq] = constraint(x);
% no errors coming from there

I have assumed the value of x=2 but it will be different in your setting.

Incorrect

% error will happen because you are not passing an input parameter
[c,ceq] = constraint();