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Re: naive question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92819] Re: [mg92781] naive question
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Tue, 14 Oct 2008 04:56:58 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

expr = Fit[{{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}, {1, x1, x2}, {x1, x2}];

Flatten[CoefficientList[expr, {x2, x1}]] // Most

{1.55556,0.555556,0.444444}

Most is used to drop the coefficient (0) of the (x1*x2) term 

Cases[expr, _?NumericQ, Infinity]

{1.55556,0.555556,0.444444}

Or using FindFit rather than Fit

{a, b, c} /. 
 FindFit[{{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}, 
  a + b*x1 + c*x2, {a, b, c}, {x1, x2}]

{1.55556,0.555556,0.444444}


Bob Hanlon

---- Francisco Gutierrez <fgutiers2002 at yahoo.com> wrote: 

=============
Dear Friends:
I am using Fit within a function, and I want it to produce only a list of
 coefficients, without the variables.
For example, if I plug into fit the following: Fit[{{1,2,3},{4,5,6},{7,8,9}},{1,x1,x2},{x1,x2}],
Mathematica produces:
1.55556+0.555556 x1+0.444444 x2
 
I want to get only the following list:
{1.55556,0.555556,0.444444}
 
It seem awfully simple, but I haven't managed.
How can I do it?
Thanks
Francisco
 


--

Bob Hanlon



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