Inner matrix dimensions must agree.

When I run this code I get Error using * Inner matrix dimensions must agree. Error in gauss_seidel (line 23) X(j)=(B(j)-A(j,1:j-1)*X(1:j-1)-A(j,j+1:N)*P(j+1:N))/A(j,j);

I can't figure out what it is. EDU>>

if true
  % 
function X=gseid(A,B,P,max1)
A = [0.07 0.18 0.15 0.24;
   0.04 0.24 0.10 0.65;
   0.54 0.42 0.54 0.10;
   0.35 0.16 0.21 0.01];
B = [10.5; 17.5; 28; 14];
P = [0;0;0;0]; % Initial Guess
max1=4; % Max number of iterations
N = length(B);
for k=1:max1
 for j=1:N
    if j==1
      X(1)=(B(1)-A(1,2:N)*P(2:N))/A(1,1);
    elseif j==N
       X(N)=(B(N)-A(N,1:N-1)*(X(1:N-1))')/A(N,N);
    else
     %X contains the kth approximations and P the (k-1)st
     X(j)=(B(j)-A(j,1:j-1)*X(1:j-1)-A(j,j+1:N)*P(j+1:N))/A(j,j);
    end
 end
 err=abs(norm(X'-P));
 relerr=err/norm(X);
 P=X'
end
X=X';
end

[dpb]

Set a breakpoint at that line and inspect

size(B(j))
size(A(j,1:j-1))

Also, NB: pass the arrays A,B,P and max1 instead of defining them inside the function (unless you did that to be self-contained for posting in which case it still won't run there being not enough inputs :) )