Matching Equation to Data

[Thomas D. Dean]

I have a problem with matching an equation to data.

I have JPL's de405 and created an oct file to interface to it.  I can 
extract data from de405 and with scatter3(), the plot looks exactly like 
what you would expect.  The orbit of Earth, or any other selected body. 
 The source for the oct file is available if anyone is interested.

I calculated the angle to the ecliptic and got 23.457 degrees, exactly 
what it should be.

I have an array with 1000 data points, D=[et,x,y,z,dx,dy,dz];  I want to 
get an equation for the plane that contains the earth's orbit.
  a*x + b*y + c*z + d = 0
so the vector x=[a, b, c, d] and,
  [D(:,2:4),ones(size(D,1),1)]*x'
is near zero for all values in D(:,2:4).

I tried looking at optim but, cannot get my head produce the correct 
arguments to the functions.

How do I do this?

Tom Dean