Index exceeds the number of array elements (1)

Dear all, how can I fix the error on ES row? I would be grateful if you help me

NDOF = 2*NN;
K = zeros(NDOF,NDOF);
for k = 1:NE
    i = CON(k,1);
    j = CON(k,2);
    dx = COORD(j,1)-COORD(i,1); 
    dy = COORD(j,2)-COORD(i,2);
    a = [-dx/L(k) -dy/L(k) dx/L(k) dy/L(k)];
    ES = a'.*EA(k)/L(k)*a;     
    for m = 1:4
        for n = 1:4
            mi = ID(k,m);
            ni = ID(k,n);
            K(mi,ni) = K(mi,ni) + ES(m,n);
        end
     end
end

[Alper Bora Sezgin]

Here is the full script,

COORD = [0 0; 2 0; 4 0; 2 2; 0 2];
CON = [1 2; 2 3; 3 4; 2 4; 4 1; 4 5];
EQ = [7 8; 5 6; 1 2; 3 4; 9 10];
NR = 4;
NE = size(CON,1);
NN = size(COORD,1);
EA = 0.0015*200*(10^9);
Pf = [0 0 0 0 0 0 0]';
Ur = [0 0 0]';

%---CALCULATION---
%SRUCTURAL INFORMATION

NOS = NE+NR-2*NN;
NOK = 2*NN-NR;

%LENGTH OF ELEMENT
L = zeros(NE,1);
for k = 1:NE
    i = CON(k,1);
    j = CON(k,2);
    dx = COORD(j,1) - COORD(i,1);
    dy = COORD(j,2) - COORD(i,2);
    L(k) = sqrt(dx^2+dy^2);
end

% ID ARRAY
ID = zeros(NE,4)
for k = 1:NE
    i = CON(k,1);
    j = CON(k,2);
    ID(k,1:2) = EQ(i,1:2);
    ID(k,3:4) = EQ(j,1:2);
end

% STIFFNESS MATRIX
NDOF = 2*NN;
K = zeros(NDOF,NDOF);
for k = 1:NE
    i = CON(k,1);
    j = CON(k,2);
    dx = COORD(j,1)-COORD(i,1); 
    dy = COORD(j,2)-COORD(i,2);
    a = [-dx/L(k) -dy/L(k) dx/L(k) dy/L(k)];
    ES = a'.*EA(k)/L(k)*a;
    for m = 1:4
        for n = 1:4
            mi = ID(k,m);
            ni = ID(k,n);
            K(mi,ni) = K(mi,ni) + ES(m,n);
        end
     end
end
K

[Jan]

I've formatted the code of your messages. Please use the code format button, thanks.

It would be useful to post a copy of the error message. It is easier to solve an error, than to guess, what the error is.

Answer 1

[Jan]

With some guessing:

EA is a scalar:

EA = 0.0015*200*(10^9);

Then you cannot access elements of EA > 1:

for k = 1:NE
    ...
    ES = a'.*EA(k)/L(k)*a;
    %           ^ Fails for k==2
end

I cannot guess, what you want to do instead.