Getting an error "Matrix Dimension must agree" in matlab program. Help me.

     for epsilon3=-1:1:1
      N_dash(1)=-0.5+epsilon3;
      N_dash(2)=-2*epsilon3;
      N_dash(3)=0.5+epsilon3;
      end
      for i=-1:1:1
          epsilon3=(i)
      lx=(epsilon3-0.5)*x(1)-(2*epsilon3)*x(2)+(epsilon3+0.5)*x(3);
      mx=(epsilon3-0.5)*y(1)-(2*epsilon3)*y(2)+(epsilon3+0.5)*y(3);
      nx=(epsilon3-0.5)*z(1)-(2*epsilon3)*z(2)+(epsilon3+0.5)*z(3);
       %%Jacobian Factor
        s=sqrt(((lx)^2)+(((mx)^2)+(((nx)^2))));
        end
      %%Tangent vector (ey) about y dirsction ly=(x(5)-x(2)); my=(y(5)-y(2)); ny=(z(5)-z(2));

      lve=sqrt(((ly)^2)+((my)^2)+((ny)^2)); %%vertical length of element ey = [ly; my; ny] / lve; for i=1:8 B_matrix(1,i)=1/s*repmat(N_dash, 3, 1) .* repelem(ey, 3, 1) %(ERROR HERE)
 end

x,y,z are constant values like 0.2132,0.9876 etc.

      Error using  .* 
  Matrix dimensions must agree.

Error in practisee2 (line 309)
B_matrix(1,i)=1/s*repmat(N_dash, 3, 1) .* repelem(ey, 3, 1)

[Walter Roberson]

Is it possible that you want to compute the dot product?

Answer 1

[Haritha]

Hi Try this B_matrix(1,i)=1/s.*repmat(N_dash, 3, 1) .* repelem(ey, 3, 1)

[Virajan Verma]

@Haritha Sorry. Not working.

[Virajan Verma]

I am stuck in this for last 2 days. Someone please help me get out of it.

[Torsten]

Before the line

B_matrix(1,i)=...

insert the lines

size(repmat(N_dash, 3, 1))
size(repelem(ey, 3, 1))

in your code and take a look at what MATLAB tells you in the output window.

If the sizes of the two arrays differ, MATLAB will complain about "Matrix dimensions must agree". Furthermore, since B_matrix(1,i) is a single scalar, the two sizes must be 1. Since this is not the case, you will get an error anyhow.

Best wishes

Torsten.

[Virajan Verma]

N_dash has size 3x3 and ey 9x1. What can i do to make their size the same??

[Torsten]

If N_dash has size 3x3, then repmat(N_dash,3,1) will produce an error. If ey has size 9x1, then repelem(ey,3,1) has size 27x1. No chance for elementwise multiplication.

And note again that the right-hand side ... of an assignment of the form

B_matrix(1,i) = ...

must have size 1x1.

Best wishes

Torsten.