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nzb109
USA
3 Posts |
 Posted - 12/30/2008 : 10:43:46 PM
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Origin Ver. and SR (Select Help-->About Origin):
Operating System:xp
Hello
I want to fit my data , using two functions as below:-
a)I know a series of (x,y) pairs for each point on x-axis
b)The second function is an polynomial function of unknown degree and coefficients.
Can i fit my data as a sum of the known (a) and unknown function(b)
Regards and Thanks
nzb
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scunque
5 Posts |
Posted - 01/13/2009 : 1:14:51 PM
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If you have plotted data, you can use that data as if it were a function. Origin does not have an 'unknown degree' polynomial function so you must use one with specific degree like Poly4 or Poly5 or the ninth degree equivalent Poly which internally is called PolyN.
So create a function with Parameter Names
a0,a1,a2,a3,a4,a5,a6,a7,a8,a9
defined as
y = book1_B(x) + polyn(x,a0,a1,a2,a3,a4,a5,a6,a7,a8,a9);
(Replace book1_b with your dataplot)
and using the parameter initialization copied from Poly.
You must use Y-Script as the Function Form.
Note that Poly requires at least 9 datapoints and you will need at least 11 points to get any degrees of freedom (i.e. error calculations)
Also Polynomial is usually a poor choice for fitting and this function will be swamped by the plotted data part. The plotted data should represent your ideal curve. |
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Curve fitting