Re: Calc formula from table
- To: mathgroup@smc.vnet.net
- Subject: [mg10834] Re: [mg10808] Calc formula from table
- From: Daniel Lichtblau <danl@wolfram.com>
- Date: Tue, 10 Feb 1998 21:01:46 -0500
- References: <199802050558.AAA14451@smc.vnet.net.>
Pieter van Wyk wrote:
>
> 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.
Simplest way I know of would be to use Fit.
In[20]:= xvals = {30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140,
150};
In[21]:= yvals = {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}; General::spell1:
Possible spelling error: new symbol name "yvals"
is similar to existing symbol "xvals".
In[22]:= data = Transpose[{xvals,yvals}];
In[23]:= Fit[data, {1,x,x^2,x^3}, x] // InputForm Out[23]//InputForm=
651.3037962053982 - 12.94513569772329*x + 0.08956081418702694*x^2 -
0.00021191724942238452*x^3
Daniel Lichtblau
Wolfram Research
- References:
- Calc formula from table
- From: Pieter van Wyk <modeltec@icon.co.za>
- Calc formula from table