# Non-Linear Least Square

• Mar 16th 2012, 06:02 AM
Baz300
Non-Linear Least Square
Hi guys,

I've been presented with a maths puzzle/equation to solve, but after some searching and an attempt at a self taught crash course I've still not been able to find a solution to this problem. So could anyone solve this please.

I need to find the approx values of a-f in this equation.

y = ax^5 - bx^4 + cx^3 - dx^2 + ex - f

Where x and y are....

x y
-15 -5,439,067
-10 -726,897
-5 -24,127
5 21,213
10 685,283
15 5,232953

If anyone could solve this that would be great thanyou.

Barry
• Mar 16th 2012, 06:49 AM
princeps
Re: Non-Linear Least Square
You can solve this system of linear equations using WolframAlpha
• Mar 16th 2012, 07:16 AM
Baz300
Re: Non-Linear Least Square
Hi thanks for the link, but unless I'm missing something (and I literally have no idea at all) but I don't think that could work out non linear regression equations (not that I know exactly what that means but I think I get the gist). There's no-where to put parameters in. Or am I wrong?
• Mar 16th 2012, 07:33 AM
princeps
Re: Non-Linear Least Square
Quote:

Originally Posted by Baz300
Hi thanks for the link, but unless I'm missing something (and I literally have no idea at all) but I don't think that could work out non linear regression equations (not that I know exactly what that means but I think I get the gist). There's no-where to put parameters in. Or am I wrong?

If you plug in values of x and y into starting equation you should obtain six equations with six unknowns (a,b,c,d,e,f)
• Mar 16th 2012, 08:51 AM
Baz300
Re: Non-Linear Least Square
Do you mean input the equation 6 times each with the different set of x and y values. I tried with one set and obviously it spouted out the equation back at me in a few different ways but no values for a to f.

Thanks Barry
• Mar 16th 2012, 09:37 AM
princeps
Re: Non-Linear Least Square
Quote:

Originally Posted by Baz300
Do you mean input the equation 6 times each with the different set of x and y values. I tried with one set and obviously it spouted out the equation back at me in a few different ways but no values for a to f.

Thanks Barry

\$\displaystyle (a,b,c,d,e,f)=(7,2,6,8,9,7)\$
• Mar 16th 2012, 10:07 AM
Baz300
Re: Non-Linear Least Square
I don't know how you did that but that's great, thanks so much for your time and patience.

Regards, Barry