Help with " Attempted to access X(2,1); index out of bounds because numel(X)=1."

Hi, so I just copy the code here... Script:

clc
clear
x1 = sym('x1','real');
x2 = sym('x2','real');
T = [x1 - x2-2;x1^2+x2-2];
J= jmat(T)
x1=1;
x2=1;
%x3=1;
%x4=1;

X = [x1; x2];
[m,n]=size(X)
eps=1e-6;
Y = [];
disp('iteracija     x1      x2      F(x1)    F(x2)     Norma')
fprintf('%5i     %11.6f %11.6f\n',0 , X(1,1), X(2,1))
i=1;
while norm(F(T,X(i)))>=eps
   X(i+1)=X(i)-DF(J,X(i)^(-1))*F(T,X(i));
   norma(i)=norm(F(T,X(:,end)));
   fprintf('%5i     %11.6f %11.6f %11.6f %11.6f %11.6f \n',i, X(1,end), X(2,end), Y(1,end),Y(2,end), norma(i))
end

function files: jmat.m

function [ R ] = jmat( T )

x1 = sym('x1','real');
x2 = sym('x2','real');

v = [x1, x2];
R= jacobian(T,v);

end

DF.m

function [ R ] = DF( J, X )

x1 = sym('x1','real');
x2 = sym('x2','real');
%x3 = sym('x3','real');
%x4 = sym('x4','real');

R=J;
x1=X(1,1);
x2=X(2,1);
R=eval(R)

end

F.m

function [ Y ] = F( T, X)

x1 = sym('x1','real');
x2 = sym('x1','real');
%x3 = sym('x3','real');
%x4 = sym('x4','real');

Y=T;
x1=X(1,1);
x2=X(2,1);
Y=eval(Y)

end

And the error is:

??? Attempted to access X(2,1); index out of bounds because numel(X)=1.

Error in ==> F at 11 x2=X(2,1);

Error in ==> lygciusistemos at 20 while norm(F(T,X(i)))>=eps

And how the hell X became (1,1) in function, when it was (2,1) in script?

I would really appreciate your help :)

And if there's something you can't understand, tell me :)

Answer 1

[Star Strider]

‘And how the hell X became (1,1) in function, when it was (2,1) in script?’

I believe that problem is simply a mistyped statement.

In F.m, you defined x1 and x2 to be the same:

F.m

function [ Y ] = F( T, X)
x1 = sym('x1','real');
x2 = sym('x1','real');

Also, X is a column-major matrix, so you should refer to its column-vector elements as:

X(:,i)

and your updates to it should be:

X(:,i+1)

(NOTE that it is best that you not use i or j as variables because MATLAB uses them for its imaginary operators. This can cause confusion if you have complex numbers.)

Answer 2

[Matt J]

Because in this expression, you passed X(i), a scalar, to F()

while norm(F(T,X(i)))

[Tautvis]

Could you tell me, how should I correct this mistake?

[Matt J]

How would I know that better than you? Is F() supposed to be able to process a scalar input X(i) or not? If so, what is the line

x2=X(2,1);

doing there in F.m ?