Hi please help me correct this error

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Abdurahman Itani
Abdurahman Itani 2017-10-12
编辑： Walter Roberson 2017-10-14
this is the error i am receiving while using the jacobian function,
Error using sym/subs>normalize
Inconsistency between sizes of
second and third arguments.
here is my code
------------------------------------------------------------------------
function [func, j] = sysNonlinearEqs(X) % X here is a vector
clc;
x = X(1)
y = X(2)
z = X(3)
%Define F(x)
syms x y z
func(1,1)= x + y - exp(-z); % Row 1 Column 1 of Vector F(x)
func(2,1)= z + x - exp(-y); % Row 2 Column 1 of Vector F(x)
func(3,1)= y + z - exp(-x); % Row 3 Column 1 of Vector F(x)
% Define Jacobian
J = jacobian(func, [x y z])
j = double(subs(J,{x, y, z}, X))
---------------------------------------------------------
i am trying to call my function in this script and the error message pops up
syms X
%global x y z
% Initial Conditions
X0 = [1; 1; 1];
maxiter = 50;
tolx = 1e-6;
%computation using the Newton Raphson Method
X= X0;
xold = X0;
for i = 1:maxiter
[func,j] = sysNonlinearEqs(X);
X = X- inv(j)*func;
err(:,i) = abs(X-xold);
xold = X;
if ( err(:,i) < tolx)
break;
end
end

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采纳的回答

Jonathan Chin
Jonathan Chin 2017-10-12
function [func, j] = sysNonlinearEqs(X)
% X here is a vector clc;
% x = X(1); y = X(2); z = X(3) ;
%Define F(x)
syms x y z
func(1,1)= x + y - exp(-z); % Row 1 Column 1 of Vector F(x)
func(2,1)= z + x - exp(-y); % Row 2 Column 1 of Vector F(x)
func(3,1)= y + z - exp(-x); % Row 3 Column 1 of Vector F(x)
% Define Jacobian
J = jacobian(func, [x y z]) ;
j = double(subs(J,{x, y, z}, X(:).')); %<- X here needs to be in row vector format
  2 个评论
Abdurahman Itani
Abdurahman Itani 2017-10-13
编辑：Abdurahman Itani 2017-10-13
i changed the code now the error is
Conversion to logical from sym is not possible.
Error in Main_Script (line 15) if ( err(:,i) < tolx)
can you please help me there?thank you
Jonathan Chin
Jonathan Chin 2017-10-14
err(:,i) is a system of equations, you might need to evaluate those values

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