source: sasview/sansmodels/src/sans/models/GuinierModel.py @ 87fbc60

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Last change on this file since 87fbc60 was 800fc80, checked in by Jae Cho <jhjcho@…>, 16 years ago

changed guinier defult rg to 60 A from 0.1 A

  • Property mode set to 100644
File size: 2.3 KB
Line 
1#!/usr/bin/env python
2"""
3    Provide I(q) = I_0 exp ( - R_g^2 q^2 / 3.0)
4    Guinier function as a BaseComponent model
5"""
6
7from sans.models.BaseComponent import BaseComponent
8import math
9
10class GuinierModel(BaseComponent):
11    """
12        Class that evaluates a Guinier model.
13   
14        I(q) = I_0 exp ( - R_g^2 q^2 / 3.0 )
15       
16        List of default parameters:
17         I_0 = Scale
18         R_g = Radius of gyration
19         
20    """
21       
22    def __init__(self):
23        """ Initialization """
24       
25        # Initialize BaseComponent first, then sphere
26        BaseComponent.__init__(self)
27       
28        ## Name of the model
29        self.name = "Guinier"
30        self.description=" I(q) = I_0 exp ( - R_g^2 q^2 / 3.0 )\
31                        List of default parameters:\
32                        I_0 = Scale\
33                        R_g = Radius of gyration"
34        ## Define parameters
35        self.params = {}
36        self.params['scale']  = 1.0
37        self.params['rg']     = 60
38
39        ## Parameter details [units, min, max]
40        self.details = {}
41        self.details['scale'] = ['cm-1', None, None]
42        self.details['rg']    = ['A', None, None]
43        #list of parameter that cannot be fitted
44        self.fixed= [] 
45    def _guinier(self, x):
46        return self.params['scale'] * math.exp( -(self.params['rg']*x)**2 / 3.0 ) 
47   
48    def run(self, x = 0.0):
49        """ Evaluate the model
50            @param x: input q-value (float or [float, float] as [r, theta])
51            @return: (guinier value)
52        """
53        if x.__class__.__name__ == 'list':
54            return self._guinier(x[0])
55        elif x.__class__.__name__ == 'tuple':
56            raise ValueError, "Tuples are not allowed as input to BaseComponent models"
57        else:
58            return self._guinier(x)
59   
60    def runXY(self, x = 0.0):
61        """ Evaluate the model
62            @param x: input q-value (float or [float, float] as [qx, qy])
63            @return: guinier value
64        """
65        if x.__class__.__name__ == 'list':
66            q = math.sqrt(x[0]**2 + x[1]**2)
67            return self._guinier(q)
68        elif x.__class__.__name__ == 'tuple':
69            raise ValueError, "Tuples are not allowed as input to BaseComponent models"
70        else:
71            return self._guinier(x)
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