source: sasview/pr_inversion/distance_explorer.py @ d67fc8d

"""
    Module to explore the P(r) inversion results for a range
    of D_max value. User picks a number of points and a range of
    distances, then get a series of outputs as a function of D_max
    over that range.
    
    This software was developed by the University of Tennessee as part of the
    Distributed Data Analysis of Neutron Scattering Experiments (DANSE)
    project funded by the US National Science Foundation. 

    See the license text in license.txt

    copyright 2009, University of Tennessee
"""
import numpy
import math
import sys

class Results:
    """
        Class to hold the inversion output parameters
        as a function of D_max
    """
    def __init__(self):
        """
            Initialization. Create empty arrays
            and dictionary of labels.
        """
        # Array of output for each inversion
        self.chi2 = []
        self.osc = []
        self.pos = []
        self.pos_err = []
        self.rg = []
        self.iq0 = []
        self.bck = []
        self.d_max = []
        ## List of errors found during the last exploration        
        self.errors = []
        
class DistExplorer(object):
    """
        The explorer class
    """
    
    def __init__(self, pr_state):
        """
            Initialization.
            
            @param pr_state: sans.pr.invertor.Invertor object
        """
        self.pr_state  = pr_state
        self._default_min = 0.8*self.pr_state.d_max
        self._default_max = 1.2*self.pr_state.d_max

        
    def __call__(self, dmin=None, dmax=None, npts=10):
        """
            Compute the outputs as a function of D_max.
            
            @param dmin: minimum value for D_max
            @param dmax: maximum value for D_max
            @param npts: number of points for D_max
        """
        # Take care of the defaults if needed
        if dmin is None:
            dmin = self._default_min
            
        if dmax is None:
            dmax = self._default_max
            
        # Results object to store the computation outputs.
        results = Results()
        
        # Loop over d_max values
        for i in range(npts):    
            d = dmin + i * (dmax - dmin)/(npts-1.0)
            self.pr_state.d_max = d
            try:
                out, cov = self.pr_state.invert(self.pr_state.nfunc)    
            
                # Store results
                iq0 = self.pr_state.iq0(out)
                rg = self.pr_state.rg(out)
                pos = self.pr_state.get_positive(out)
                pos_err = self.pr_state.get_pos_err(out, cov)
                osc = self.pr_state.oscillations(out)
            
                results.d_max.append(self.pr_state.d_max)
                results.bck.append(self.pr_state.background)
                results.chi2.append(self.pr_state.chi2)
                results.iq0.append(iq0)
                results.rg.append(rg)
                results.pos.append(pos)
                results.pos_err.append(pos_err)
                results.osc.append(osc)           
            except:
                # This inversion failed, skip this D_max value
                results.errors.append("ExploreDialog: inversion failed for D_max=%s\n %s" % (str(d), sys.exc_value))
            
        return results