Exponential growth curve-fitting
Exponential growth curve-fitting
(OP)
Hi, i have got a bunch of data points, which i want a curve fitted to. The function for the curve is y= b*a^x . Now, i have tried genfit and expfit, but they find coeffs for y=a*e^(b*x) and y=b*x^b. How do get the coeffs for y= b*a^x?





RE: Exponential growth curve-fitting
RE: Exponential growth curve-fitting
RE: Exponential growth curve-fitting
http://collab.mathsoft.com/read?98663,11
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RE: Exponential growth curve-fitting
The second element is the first derivative of the first element with respect to the first variable: u2^x
The third element is the first derivative of the first element with respect to the second variable: u1*x*u2^x-1
Here's how the function vector looks. I included the "[" below as that's what you type to get the subscript. The "T" at the end denotes a transposed array.
F(x,u)=(u[1*(u[2)^x (u[2)^x u[1*x*(u[2)^x-1))T
p=genfit(vx,vy,g2,F)
vx and vy are your data point vectors
g2 is a two element guess