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yi_wang123@yahoo.com
United Kingdom
1 Posts |
 Posted - 01/20/2015 : 07:44:30 AM
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Origin Ver. and Service Release (Select Help-->About Origin):
Operating System:
Dear Officer from OriginLab,
i am a current user of OriginPro 9.1. i have a machine compliance for simple compression testing. I used origin to fit the compliance experiment data and get an fitting equition in 6th order of polynomial:
6th Order Polynomial (20/01/2015 12:07:27)
Equation: y = Intercept + B1*x + B2*x^2 + B3*x^3 + B4*x^4 + B5*x^5 + B6*x^6
Weighting: No Weighting
Value Error
Intercept -26.53498 1.55894
B1 4944.41312 111.19068
B2 453105.5364 2704.9436
B3 -3.57E+06 29877.63296
B4 1.50E+07 164301.4571
B5 -3.17E+07 438339.2647
B6 2.68E+07 451894.1317
Reduced Chi-Sqr 121.57603
R-Square 0.99999
this is perfect for the compliance test. For test purpose, i have to inverse the fitting equation in format of x = f'(y) to work out x and subtract each testing compression displacement to get real displacement.
I know y value and fitting expression, my question is that, how can i get a expression for x = f'(y) or how can i directly convert this 6th Order Polynomial into x = f'(y) and feed my purpose?
many thanks
Yi WANG
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jasonzhao
China
262 Posts |
Posted - 01/20/2015 : 10:11:20 PM
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Hello,
As your describe, you have the equation:
Equation: y = Intercept + B1*x + B2*x^2 + B3*x^3 + B4*x^4 + B5*x^5 + B6*x^6
and B1 to B6 is solved by using nonlinear fitting.
now, you want to transfer it to the inverse function, and applied differentiate to new y (original x).
Then, get the value for specific y.
Image below shows the process of solving such problem in numerical method by:
1. Construct XY for function above with small interval.
2. Exchange XY.
3. Apply the differentiate to new y (original x).
4. Use interpolate to get the specific value.
I will provide further details if you think this numerical method is acceptable. However, the expression for x = f'(y) can not be obtained.
Best regards,
Jason Zhao
OriginLab Tech Service |
Edited by - jasonzhao on 01/20/2015 10:25:09 PM |
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lkb0221
China
497 Posts |
Posted - 01/21/2015 : 2:55:10 PM
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Hi,
We cannot give the inverse formula directly, but you can turn on Find X by Y in both poly-fit or NLfit dialog. You can thus type in your desired Y values in that new created worksheet and the software will calculate corresponding X values for you.
Zheng
OriginLab |
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curve fitting for compliance in compression test