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Problems with functions

 From: mat_hunt Subject: Problems with functions Date: Tue, 19 Jul 2016 13:37:14 -0700 (PDT)

```I have defined a function:

function  y=f(x)
y_1=x(1)-x(2)+x(3)-2;
y_2=2*x(1)-x(2)+x(3)-3;
y_3=2*x(1)+x(2)-x(3)-1;
y=[y_1 y_2 y_3];
endfunction

and I have written a function to compute the Jacobian of that function:

function J=jacobian(func,x)
% computes the Jacobian of a function
n=length(x);
fx=feval(func,x);
eps=1.e-8; % could be made better
xperturb=x;
for i=1:n
xperturb(i)=xperturb(i)+eps;
J(:,i)=(feval(func,xperturb)-fx)/eps;
xperturb(i)=x(i);
endfor;
endfunction

when I use the command:

jacobian(f,[1 1 1])

I get the error:

error: 'x' undefined near line 2 column 5
error: called from:
error:   /home/mat/Matlab programs/f.m at line 2, column 4
error: evaluating argument list element number 1

What is going on? The code was working perfectly fine 10 minutes ago and now
it's throwing up errors.

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```