Incorrect value in MinimizerResult.init_values

[schtandard]

First Time Issue Code

Yes, I read the instructions and I am sure this is a GitHub Issue.

Description

Using the simple example from the documentation and printing result.init_values (or result.init_vals) as in the MWE below reveals an incorrect initial value for amp. It should be 10 but it is 10.954451150103322.

A Minimal, Complete, and Verifiable example

import numpy as np

from lmfit import Minimizer, Parameters, report_fit

# create data to be fitted
x = np.linspace(0, 15, 301)
np.random.seed(2021)
data = (5.0 * np.sin(2.0*x - 0.1) * np.exp(-x*x*0.025) +
        np.random.normal(size=x.size, scale=0.2))


# define objective function: returns the array to be minimized
def fcn2min(params, x, data):
    """Model a decaying sine wave and subtract data."""
    amp = params['amp']
    shift = params['shift']
    omega = params['omega']
    decay = params['decay']
    model = amp * np.sin(x*omega + shift) * np.exp(-x*x*decay)
    return model - data


# create a set of Parameters
params = Parameters()
params.add('amp', value=10, min=0)
params.add('decay', value=0.1)
params.add('shift', value=0.0, min=-np.pi/2., max=np.pi/2.)
params.add('omega', value=3.0)

# do fit, here with the default leastsq algorithm
minner = Minimizer(fcn2min, params, fcn_args=(x, data))
result = minner.minimize()

# calculate final result
final = data + result.residual

# write error report
report_fit(result)

# now print the inital values
print(result.init_values)

This gives the output

[[Fit Statistics]]
    # fitting method   = leastsq
    # function evals   = 59
    # data points      = 301
    # variables        = 4
    chi-square         = 12.1867036
    reduced chi-square = 0.04103267
    Akaike info crit   = -957.236198
    Bayesian info crit = -942.407756
[[Variables]]
    amp:    5.03087926 +/- 0.04005805 (0.80%) (init = 10)
    decay:  0.02495454 +/- 4.5395e-04 (1.82%) (init = 0.1)
    shift: -0.10264934 +/- 0.01022298 (9.96%) (init = 0)
    omega:  2.00026304 +/- 0.00326184 (0.16%) (init = 3)
[[Correlations]] (unreported correlations are < 0.100)
    C(shift, omega) = -0.785
    C(amp, decay)   = 0.584
    C(amp, shift)   = -0.118
{'amp': 10.954451150103322, 'decay': 0.1, 'shift': 0.0, 'omega': 3.0}

report_fit correctly reports an initial value of 10 for amp but result.init_values does not.

Version information

Python: 3.9.13 | packaged by conda-forge | (main, May 27 2022, 16:50:36) [MSC v.1929 64 bit (AMD64)]

lmfit: 1.0.3, scipy: 1.9.3, numpy: 1.23.4,asteval: 0.9.27, uncertainties: 3.1.7

[newville]

@schtandard OK, thanks... that's not good!

It looks to me like that is still the "internal value", before bounds are applied. I'll check that out.