More locking of values.
This actually shows, that errors should be estimated from the Direct Jacobian. Not, the chi2 Jacobian.
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 2014-08-28
Parent: [r25409]
Child: [r25411]
