Any MATLAB users on here?

[JewishBacon]

Here is a matlab code I am working on. It needs to run this line equation and then output each iteration of "line" into the matrix below. I should be able to create this matrix without typing in all the values.  BUT i get an error of 

 

"??? Undefined function or method 'y' for input arguments of type 'double'.."

 

 

while i<=6;

 

line(i)=.6*y(i+1)+(-2.12)*y(i)+1.4*y(i-1);

 

    

  

  i=i+1;

end

 

% MATRIX=[-2.12      .6       0       0        0

%          1.4      2.12     .6       0        0

%          0        1.4     -2.12    .6        0

%          0         0       1.4     -2.12   -.6];

 

rref(MATRIX)

 

 

 

 

thanks in advance