Got the Quasi-Newton BFGS to work.
This uses only the gradient, this gets the same results as 2000 Monte-Carlo with simplex and scipy.optimize.leastsq.
Error estimation still not provided.
task #7822(https://gna.org/task/index.php?7822): Implement user function to estimate R2eff and associated errors for exponential curve fitting.
Authored by: tlinnet 2014-08-26
Parent: [r25285]
Child: [r25287]
