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MathGroup Archive 1998

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Re: Calc formula from table



Hi

x={30, 40 , 50 ,  60, 70 , 80, 90, 100, 110,    120,    130,  140, 
150}; y={338.7, 263.5, 198.6, 150.5 , 114.7, 80.3, 55.5, 41.9, 30.2,
19.3, 16.5,   12.4, 10.1};

data=Transpose[{x,y}];
fun=Fit[data,{1,X,X^2,X^3},X]

return

651.3037962048336 - 
  12.94513569797418*X + 
  0.0895608141903066*X^2 - 
  0.0002119172494346388*X^3

Is this OK four You?

Hope that helps
  Jens


> Could anyone help me: I need to know how to calculate a third order
> parabolic
> formula from a table. I.o.w. I have a table of data and I need a manual
> way to calculate the formula for the curve of the data . 3rd order
> formula to be obtained:
> Y=AX**3 + BX**2 + CX + D
> 
> example data:
> y = 338.7    263.5    198.6    150.5    114.7    80.3    55.5    41.9
> 30.2    19.3    16.5  12.4 10.1
> x=  30        40            50        60        70        80 90       
> 100    110    120    130  140  150
> 
>     answer: Y=-0.0002X**3 + 0.0896X**2 -12.945X +651.3
> 
> I need a manual method to calculate this formula.
> 
> Can it be done without using integration/differentiation. Maybe lin log
> exp?
> 
> Answers will be appreciated. Regards, Pieter.
> 
> 



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