03-25-2009 05:21 AM
Hello,
I don’t understand how using the General Polynomial fit function. I found inaccurate coefficients (I’m beginner with Labview)
I need to calculate the coefficients (A, B, C, D) for this equation: Y = A+BX+CX^2+DX^3.
With Excel I found 7 points to test the coefficient resolution with the Regression Solver.vi
The Regression Solver Results are different if I give 4, 5, 6 or 7 knowing points !!!
4 pts => y = -301.785E+0 + 4.261E+0x - 16.342E-6x^2 + 16.001E-12x^3
5 pts => y = +491.811E+3 - 380.684E-3x - 1.888E-6x^2 +
1.137E-12x^3
6 pts => y = +491.694E+3 - 379.525E-3x - 1.892E-6x^2 + 1.140E-12x^3
7 pts => y = -106.524E+3 + 2.334E+0x - 1.945E-6x^2 + 3.032E-12x^3
Why with 4 and 7 points the coefficients are wrong?
For helping you how I generate those results, you will found an Excel File and the VI in attachment.
Thanks a lot for your helps
Mark
Solved! Go to Solution.
03-25-2009 07:25 AM
I have the solution.
I use an another algorithm !! Only one algorithm give wrong results in a particular way and it is the default: SVD
Mark