Curve-fit hyperbolic function in Excel?
Lawrence P. Casson
to a hyperbolic function (ie. y=A*x/(1+B*x) )? If necessary, I'll attempt
one myself, but if one is available, so much the better. I'm attempting
to plot flourescence quenching data and to estimate Q-max. I figure that
anything that can be implemented in Excel can be used by everyone in my
lab.
Thanks,
Larry
--
Lawrence P. Casson
lpca...@phoenix.princeton.edu
Gary Rudnick
I always did this by using the solver. You create 2 columns
with your real data, x and y, and a third column with y(i)
calculated using x(i) and the equation you want. The
parameters for the equation are stored in some other cells.
Now make another column which contains the absolute difference
between the real and calculated y values and at the bottom of
that column, the sum of the differences. The solver can vary
the parameters to minimize the sum of the differences.
Good Luck!
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Department of Pharmacology |fax (203) 785-7670
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What separates the men from the boys is the price of their toys.
Dietmar Tietz
> Is anyone aware of a macro or plugin for Excel that will fit data points
> to a hyperbolic function (ie. y=A*x/(1+B*x) )? If necessary, I'll attempt
> one myself, but if one is available, so much the better. I'm attempting
> to plot flourescence quenching data and to estimate Q-max. I figure that
> anything that can be implemented in Excel can be used by everyone in my
> lab.
>
> Thanks,
> Larry
>
> lpca...@phoenix.princeton.edu
>
> --
> Lawrence P. Casson
> lpca...@phoenix.princeton.edu
>
>
>
If Excel won't do, you may try MacCurveFit 1.0.7. It is shareware and
available on gopher, use Veronica to search for it. MacCurveFit
allows you to specify your own function.
Best regards,
Dietmar Tietz
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* Biostatistics, Justus-Liebig-University *
* Ludwigstr. 27, D-35390 Giessen, Germany *
* Phone: +49-(641)-702-6015 *
* Fax: +49-(641)-702-5995 *
* Email: Dietma...@Uni-Giessen.de *
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David McCaskill
lpca...@phoenix.princeton.edu wrote:
> Is anyone aware of a macro or plugin for Excel that will fit data points
> to a hyperbolic function (ie. y=A*x/(1+B*x) )? If necessary, I'll attempt
> one myself, but if one is available, so much the better. I'm attempting
> to plot flourescence quenching data and to estimate Q-max. I figure that
> anything that can be implemented in Excel can be used by everyone in my
> lab.
Funny enough the latest issue of Macworld (think it's the Oct issue)
contains a tip towards the back that describes exactly how to do that sort
of thing using the Solver that's included with Excel. I played with it a
bit last weekend fitting some mock data to the Michaelis Menten eq'n and
it seemed to do fine. Haven't had a chance to compare it with the results
I get from SigmaPlot though and I don't have enough of a math background
to know how Excel's method of calculating user defined curve fits compares
with how other programs do it. FWIW Excel was much slower at doing the
calculations than SigmaPlot on our Mac Centris 610 (20MHz 68LC040), so for
large data sets I'm not sure how quickly it will perform.
--
David McCaskill mcca...@mail.wsu.edu
Institute of Biological Chemistry
Washington State University
Pullman, WA