MATLAB: “Subscripted assignment dimension mismatch”

dimensions mismatcherror

Hello,
Here is part of the code in which I can't avoid the following error: "Subscripted assignment dimension mismatch" at line 115. I do not have this error and the code runs fine, when I take away the main loop for the incremental load and instead have just one predefined value. If anyone can help, I will highly appreciate! If necessary I will send the whole code by mail.
Regards, Pavlin
CODE
for increment = 1:incmax
    q_total=q_total+q_incr;
    K(beam_DOFs,beam_DOFs)=0;
    F(beam_DOFs,1)=0;
    for el_y=1:beam_el_y
        y1=(W/beam_el_y)*(el_y-1);
        y3=y1+W/beam_el_y;
        for el_x=1:beam_el_x
            x1=(L/beam_el_x)*(el_x-1);
            x3=x1+L/beam_el_x;
            i1=(beam_el_y+1)*(el_x-1)+el_y;
            i2=i1+beam_el_y+1;
            el_DOFs=[2*i1-1; 2*i1 ; 2*i2-1 ; 2*i2; 2*i2+1; 2*i2+2; 2*i1+1; 2*i1+2];
            Em=(E_el(el_x,el_y)/(1-nu^2))*[1  nu 0
                                           nu 1  0
                                           0  0  (1-nu)/2];
            Ke=Q4_stiffness(x1,x3,y1,y3,Em,T);
            K(el_DOFs,el_DOFs)=K(el_DOFs,el_DOFs)+Ke;
        end
    end
    all_DOFs=1:beam_DOFs;
    fixed_DOFs_y=beam_DOFs;
    fixed_DOFs_x=1:2:2*(beam_el_y+1);
    fixed_DOFs=union(fixed_DOFs_x,fixed_DOFs_y);
    free_DOFs=setdiff(all_DOFs,fixed_DOFs);
    F(2,1)=-q_total;
    U(free_DOFs,:)=K(free_DOFs,free_DOFs)\F(free_DOFs,:);
    U(fixed_DOFs,:)=0;
    ver_DOFs_top_side=2*(beam_el_y+1):2*(beam_el_y+1):beam_DOFs;
    U(ver_DOFs_top_side,:);
    ver_DOFs_top_side2=ver_DOFs_top_side;
    ver_DOFs_top_side2(:,end)=[];
    U(2,1);
    U_tot=U_tot+U(2,1);
    for el_y=1:beam_el_y
        y1=(W/beam_el_y)*(el_y-1);
        y3=y1+W/beam_el_y;
        for el_x=1:beam_el_x
            x1=(L/beam_el_x)*(el_x-1);
            x3=x1+L/beam_el_x;
            i1=(beam_el_y+1)*(el_x-1)+el_y;
            i2=i1+beam_el_y+1; % i2=(DCB_y+1)*el_x+el_y;
            el_DOFs=[2*i1-1; 2*i1 ; 2*i2-1 ; 2*i2; 2*i2+1; 2*i2+2; 2*i1+1; 2*i1+2];
            Em=(E_el(el_x,el_y)/(1-nu^2))*[1  nu 0
                                           nu 1  0
                                           0  0  (1-nu)/2];
            el_displ=U(el_DOFs);
            el_stress=zeros(3,8);
            el_strain=zeros(3,8);
            [el_stress el_strain]=Q4_stress(x1,x3,y1,y3,Em,el_displ);
            Sigma_xx(el_x,el_y)=el_stress(1,1);
            Sigma_yy(el_x,el_y)=el_stress(2,1);
            Sigma_xy(el_x,el_y)=el_stress(3,1);
            x(el_x,el_y)=x1; % For the mesh plot

            y(el_x,el_y)=y1; % For the mesh plot
            Sigma_xx_tot(el_x,el_y) = Sigma_xx_tot(el_x,el_y) + Sigma_xx(el_x,el_y);
            Sigma_yy_tot(el_x,el_y) = Sigma_yy_tot(el_x,el_y) + Sigma_yy(el_x,el_y);
            Sigma_xy_tot(el_x,el_y) = Sigma_xy_tot(el_x,el_y) + Sigma_xy(el_x,el_y);
            S11 = 2*Sigma_xx_tot(el_x,el_y)/3 - Sigma_yy_tot(el_x,el_y)/3;
            S22 = 2*Sigma_yy_tot(el_x,el_y)/3 - Sigma_xx_tot(el_x,el_y)/3;
            S12 = Sigma_xy_tot(el_x,el_y);
            Sigma_von_Mises = sqrt(3*(S11^2+S22^2+3*S12^2)/2);
            if  Sigma_von_Mises > Sigma_y;
                E_el(el_x,el_y)=E/10;
            else
                E_el(el_x,el_y)=E;
            end
        end
    end
last_x=zeros(1,beam_el_y);
LINE 115 last_x(1,:)=x(end,:)+L/beam_el_x;
x=[x;last_x]; x=[x,x(:,end)]; last_y=zeros(1,beam_el_y); last_y(1,:)=y(end,:); y=[y;last_y]; y=[y,y(:,end)+W/beam_el_y];

Best Answer

This error occurs, much like the message tells you, when you try to put the wrong number (or shape) of items into an array. Here is a simple example:
H = zeros(6);
try
    H(:,1) = rand(2,3);  % Wrong shape.
catch
    fprintf('%s\n',lasterr)
end
try
    H(:,1) = rand(7,1);  % Wrong number.
catch
    fprintf('%s\n',lasterr)
end
H(:,1) = rand(6,1)  % Correct shape and number!
Related Question