Errors : undefined function or variable, too many output arguements- do not know why..please help. Struggling.

I really am struggling with Matlab. Actally, I have a Mathcad code which has to be converted into Matlab.

See this code;

% This the input file.
% We first accept the inputs of: nodal coordinates, element
% connectivity,material properties through an xls file.

% N_C = nodal coordinates.
% E_C = element connectivity.
% A_E=  area of cross section per element.
% E_E = modulus of elasticity per element.
% rho_E = density of the material per element.
% N_NBC = number of nodes where Neumann boundary conditions are introduced.
% p = order of approximation.
% n_dof = number of degrees of freedom

p=1;

n_dof=p+1;

N_C=xlsread('C:\Users\Ajay Taneja\vibrations\free_vibrations_program\matlab_input_free_vibrations_1','Sheet1');

E_C=xlsread('C:\Users\Ajay Taneja\vibrations\free_vibrations_program\matlab_input_free_vibrations_1','Sheet2');

xlRange='A1:A2';

A_E=xlsread('C:\Users\Ajay Taneja\vibrations\free_vibrations_program\matlab_input_free_vibrations_1','Sheet3',xlRange);

xlRange='B1:B2';

E_E=xlsread('C:\Users\Ajay Taneja\vibrations\free_vibrations_program\matlab_input_free_vibrations_1','Sheet3',xlRange);

xlRange='C1:C2';

rho_E=xlsread('C:\Users\Ajay Taneja\vibrations\free_vibrations_program\matlab_input_free_vibrations_1','Sheet3',xlRange);

no_of_elements=size(E_C);
E_k=zeros(50,2,2);
E_k_temp=zeros(2,2);

for i=1:no_of_elements

      E_k_temp=ElemenStiffness(i);

      for j=1:2

          for k=1:2

              E_k(i,j,k)=E_k_temp(j,k);

          end
      end

end

I have in the Element Stiffness file

function ElementStiffness(element_no)

E_k(element_no);

ElementStiffness=E_k;

end

function Length

dimensions=size(E_C);

for i=1,dimensions(1)

      node1=E_C(i,1);
      node2=E_C(i,2);
      x2=N_C(node2,1);
      x1=N_C(node1,1);
      y2=N_C(node2,2);
      y1=N_C(node1,2);
      z1=N_C(node1,3);
      z2=N_C(node2,3);

      Len(i,1)=(x2-x1)^2+(y2-y1)^2+(z2-z1)^2;
      Len(i,1)=(Len(i,1))^0.5;

end

Length=Len;

end

function Jacobian(element_no)

len=Length;

% return Length(element_no,1)/2;

end

function NumberOfGaussPoints

n_dof=p+1;

q=max(2*p-1,2*p,p+2);

if (mod(q,2)==0)

      NumberOfGaussPoints= q+2/2;

else
    NumberOfGaussPoints= (q+1)/2;

end

end

function E_k(element_no)

for s=1:n_dof

      for t=1:n_dof

          k(s,t)=0;

      end

      for i=1,no_gp

          all_gauss_pts_wts=SW(no_gp);
          gauss_pt=all_gauss_pts_wts(i,1);
          gauss_wt=all_gauss_pts_wts(i,2);

          for s=1:n_dof

              for t=1:n_dof

                  dN=LagrangianShapeFnsDerivatives(p,gauss_pt);
                  k(s,t)=k(s,t)+(dN(s,1)*dN(t,1)*A(element_no)*E(element_no)*(1/J));

              end

          end

      end

end

E_k=k;

end

and then;

function SW=GaussPoints(no_gp)

SW := array(1..6,1..2);

if(no_gp==1)then

      SW(1,1)=0;
      SW(1,2)=2;

else if(no_gp==2)then

      SW(1,1)=0.577350269189626;
      SW(1,2)=1;
      SW(2,1)=-0.577350269189626;
      SW(2,2)=1;

      else if(no_gp==3)then

      SW(1,1)=0;
      SW(1,2)=0.888888888888889;
      SW(2,1)=0.774596669241483;
      SW(2,2)=0.555555555555556;
      SW(3,1)=-0.774596669241483;
      SW(3,2)=0.555555555555556;

          elseif (no_gp==4)then

              SW(1,1)=0.339981043583856;
              SW(1,2)=0.652145154862526;
              SW(2,1)=-0.339981043583856;
              SW(2,2)=0.652145154862526;
              SW(3,1)=0.861136311590453;
              SW(3,2)=0.3478548415137454;
              SW(4,1)=-0.861136311590453;
              SW(4,2)=0.3478548415137454;

          else(no_gp==5)then
              SW(1,1)=0.9061798459;
              SW(1,2)=0.2369268851;
              SW(2,1)=-0.9061798459;
              SW(2,2)=0.2369268851;
              SW(3,1)=0.5384693101;
              SW(3,2)=0.5688888889;
              SW(4,1)=-0.5384693101;
              SW(4,2)=0.5688888889;
              SW(5,1)=0;
              SW(5,2)=0.1713244924;           

end
When I compile the code, I get the following error in input file
>> Input_file
Error using ElementStiffness
Too many output arguments.

Error in Input_file (line 40) E_k_temp=ElementStiffness(i);

Also, the next file ElementStiffness has error

>> ElementStiffness(element_no) Undefined function or variable 'element_no'.

I really do not know what is the problem

I have attached my 3 .m files and the xls file. IF someone can help, I shall be extremely ever grateful.

Answer 1

[Walter Roberson]

In MATLAB, if you want to return a value from a variable, the syntax is not that you assign a value to the name of the function. Instead you use (for example)

function [ek] = ElementStiffness(element_no)  
  ek = E_k(element_no);
end

That is, you list the output variables on the left side of the "=" in the function statement, and you assign values to those output variables somewhere in your routine.