Nelder-Mead downhill simplex
==============================

.. currentmodule:: PyAstronomy.funcFit
.. autoclass:: NelderMead
   :members:
   :private-members:

Example: Application of the NelderMead class
----------------------------------------------

::
    
    from PyAstronomy import funcFit as fuf
    import numpy as np
    
    # Construct the fitter
    nm = fuf.NelderMead()
    
    # Get a GaussFit object ...
    gf = fuf.GaussFit1d()
    gf.thaw(["A", "mu"])
    # ... and define some initial values.
    gf["A"] = 5.0
    gf["mu"] = 2.0
    gf["sig"] = 1.0
    
    # Construct some "data" ...
    x = np.arange(100)/20.
    y = gf.evaluate(x) + np.random.normal(0.0, 0.08, len(x))
    yerr = np.ones(len(x)) * 0.08
    # ... and define a "data set" object
    ds = fuf.FufDS(x, y, yerr=yerr)
    
    # On purpose, we vail our knowledge about the correct
    # parameters
    gf["A"] = 1.0
    gf["mu"] = 1.0
    
    # We carry out the fit. In particular, the squared
    # distance between the model and the data is minimized
    # (sqrdiff).
    bfpars = nm.fit(gf, ds, objf="sqrdiff", maxIter=100)
    # Have a look at the result
    print "Best-fit parameters: ", bfpars
    print
    # Have a look at the entire fit object
    gf.parameterSummary()
    
    
    print
    # Again, we change the starting parameters. Note that ...
    gf["A"] = 1.0
    # ... mu has been set to zero.
    gf["mu"] = 0.0
    
    # To allow the construction of an appropriate start simplex,
    # we need to provide an "initDelta" for mu, which should
    # reflect the typical scale of the problem.
    bfpars = nm.fit(gf, ds, objf="chisqr", initDelta={"mu": 0.1})
    print "Second fit, best-fit parameters: ", bfpars