Index exceeds matrix dimensions in very simple equation

x = sym('x', [1 3*N], 'real');
N=4;
L=1;
for i=2:N+1
    pl(:,:,i)=L*[(cos(x(3*i-2))*(1-cos(x(3*i-1))))/x(3*i-1) (sin(x(3*i-2))*(1-cos(x(3*i-1))))/x(3*i-1) sin(x(3*i-1))/x(3*i-1)]';
end

dear all i dont understand why i get Index exceeds matrix dimensions error in this code

i really appreciated if you could help me

Answer 1

[Birdman]

When i=4, x(3*i-1) means you try to reach 13th element of x, but you defined its size as [1 12].

When i=5, x(3*i-1) and x(3*i-2) both try to reach 14th and 13th element of x, yet which is invalid.

Either change size of x, or change the value N accordingly.