Interpolation / Curve fitting / Empirical formula

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satendra kumar
satendra kumar 2011-11-16
Hii, I have an Eq.- M=A[P^a]*[Q^b]*[R^c] From experiments the value of M,P,Q,R is known to me. Now i need to find the value of A,a,b,c... Can anyone tell me how to solve this problem

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回答（1 个）

Andrew Newell
Andrew Newell 2011-11-17
Take the logarithms of both sides, so you have a linear regression problem. How you solve that depends on whether you have the Statistics Toolbox.
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satendra kumar
satendra kumar 2011-11-17
Thanks for your ans, but In my prblm the power may be anything not like 1,2,3,4. The values of a,b,c can be anything as .5,.6 so I think its not a linear regression problem.
Kindly send me some more suggestions
Andrew Newell
Andrew Newell 2011-11-17
If you take the logarithms, you get:
log(M) = log(A) + a*log(P) + b*log(Q) + c*log(R).
That's a linear equation, equivalent to
y = r +a*x1 + b*x2 +c*x3.
That's a linear equation in the variables y=log(M), x1=log(P), etc., and there is certainly no requirement that r, a, b and c be integers.

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