source: sasview/src/sas/models/LorentzModel.py @ 79492222

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Last change on this file since 79492222 was 79492222, checked in by krzywon, 8 years ago

Changed the file and folder names to remove all SANS references.

  • Property mode set to 100644
File size: 2.8 KB
Line 
1#!/usr/bin/env python
2"""
3    Provide F(x) = scale/( 1 + (x*L)^2 ) + bkd
4    Lorentz (Ornstein-Zernicke) function as a BaseComponent model
5"""
6
7from sas.models.BaseComponent import BaseComponent
8import math
9
10class LorentzModel(BaseComponent):
11   
12    """
13        Class that evaluates a Lorentz (Ornstein-Zernicke) model.
14       
15        F(x) = scale/( 1 + (x*L)^2 ) + bkd
16       
17        The model has three parameters:
18            L     =  screen Length
19            scale  =  scale factor
20            bkd    =  incoherent background
21    """
22       
23    def __init__(self):
24        """ Initialization """
25       
26        # Initialize BaseComponent first, then sphere
27        BaseComponent.__init__(self)
28       
29        ## Name of the model
30        self.name = "Lorentz"
31        self.description="""Lorentz (Ornstein-Zernicke) model.
32        F(x) = scale/( 1 + (x*L)^2 ) + bkd
33       
34        The model has three parameters:     
35        L     =  screen Length\n\
36        scale  =  scale factor\n\
37        bkd    =  incoherent background"""
38        ## Define parameters
39        self.params = {}
40        self.params['length']      = 50.0
41        self.params['scale']       = 1.0
42        self.params['background']  = 0.0
43
44        ## Parameter details [units, min, max]
45        self.details = {}
46        self.details['length']     = ['[A]', None, None]
47        self.details['scale']      = ['', None, None]
48        self.details['background'] = ['[1/cm]', None, None]
49        #list of parameter that cannot be fitted
50        self.fixed= []     
51    def _lorentz(self, x):
52        """
53            Evaluate F(x) = scale/( 1 + (x*L)^2 ) + bkd
54           
55        """
56        return self.params['scale']/( 1 + math.pow((x * self.params['length']),2))\
57                + self.params['background']
58       
59   
60    def run(self, x = 0.0):
61        """ Evaluate the model
62            @param x: input q-value (float or [float, float] as [r, theta])
63            @return: (Lorentz value)
64        """
65        if x.__class__.__name__ == 'list':
66            return self._lorentz(x[0])
67        elif x.__class__.__name__ == 'tuple':
68            raise ValueError, "Tuples are not allowed as input to BaseComponent models"
69        else:
70            return self._lorentz(x)
71   
72    def runXY(self, x = 0.0):
73        """ Evaluate the model
74            @param x: input q-value (float or [float, float] as [qx, qy])
75            @return: Lorentz value
76        """
77        if x.__class__.__name__ == 'list':
78            q = math.sqrt(x[0]**2 + x[1]**2)
79            return self._lorentz(q)
80        elif x.__class__.__name__ == 'tuple':
81            raise ValueError, "Tuples are not allowed as input to BaseComponent models"
82        else:
83            return self._lorentz(x)
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