# Re: Constrain a polynomial trend line to intercept y-axis horizontally

• From: Mike Simms <mesimms gmail com>
• To: gnumeric-list gnome org
• Subject: Re: Constrain a polynomial trend line to intercept y-axis horizontally
• Date: Mon, 17 Jun 2013 06:07:00 -0700 (PDT)

```Thanks Jean and John,

I guess most of the time I'm trying to fit the a quadratic which intersects
the y-axis with a slope of zero.
Suppose I have my 'y's in A1:A1000 and my 'x's in B1:B1000. I prepare
C1=B1^2 and copy down to C1000. Then i select three cells in a row and type
=linest(A1:A1000,B1:C1000,TRUE) and I get the same coefficients for x^2, x
and the constant term that I see when I display the equation on the chart.
x^2 coeff is 0.062222
x coeff is 0.82926
constant is 23.70

So far so good. I'm not sure where/how to type the array constant {0,2} into
the cell, if i type
=linest(A1:A1000^{0,2},b1:c1000,TRUE) then I get some large numbers which
can't be right.
first cell: 13.04667
second cell 77.1289

Am I typing this formula withe array constant correctly?

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```