source: sasview/sansmodels/src/sans/models/CorrLengthModel.py @ 87f51eb

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Last change on this file since 87f51eb was 18695bf, checked in by Jae Cho <jhjcho@…>, 14 years ago

replaced math.pow to numpy.power since math.pow is not working with list of x values(remember we use the list in fitting for speed)

  • Property mode set to 100644
File size: 3.2 KB
Line 
1#!/usr/bin/env python
2"""
3CorrLengthModel function as a BaseComponent model
4"""
5
6from sans.models.BaseComponent import BaseComponent
7from numpy import power
8
9class CorrLengthModel(BaseComponent):
10    """
11    Class that evaluates a CorrLengthModel.
12    I(q) = I(q) = scale_p/pow(q,exponent)+scale_l/
13    (1.0 + pow((q*length_l),exponent_l) )+ background
14    """
15       
16    def __init__(self):
17        """ Initialization """
18       
19        # Initialize BaseComponent first, then sphere
20        BaseComponent.__init__(self)
21       
22        ## Name of the model
23        self.name = "CorrLength"
24        self.description="""I(q) = scale_p/pow(q,exponent)+scale_l/
25            (1.0 + pow((q*length_l),exponent_l) )+ background
26             List of default parameters:
27             scale_p = Porod term scaling
28             exponent_p = Porod exponent
29             scale_l = Lorentzian term scaling
30             length_l = Lorentzian screening length [A]
31             exponent_l = Lorentzian exponent
32             background = Incoherent background
33        """
34        ## Define parameters
35        self.params = {}
36        self.params['scale_p']  = 1.0e-06
37        self.params['exponent_p']     = 3.0
38        self.params['scale_l']  = 10.0
39        self.params['length_l']     = 50.0
40        self.params['exponent_l']     = 2.0
41        self.params['background']     = 0.1
42        ## Parameter details [units, min, max]
43        self.details = {}
44        self.details['scale_p'] = ['', None, None]
45        self.details['exponent_p'] =  ['', None, None]
46        self.details['scale_l']  =  ['', None, None]
47        self.details['length_l']  =   ['A', None, None]
48        self.details['exponent_l']  =   ['', None, None]
49        self.details['background']   =  ['[1/cm]', None, None]
50
51        #list of parameter that cannot be fitted
52        self.fixed= [] 
53    def _corrlength(self, x):
54        """
55        Model definition
56        """
57        inten = self.params['scale_p']/pow(x,self.params['exponent_p'])
58        inten += self.params['scale_l']/(1.0 + \
59                power((x*self.params['length_l']),self.params['exponent_l']))
60        inten += self.params['background']
61
62        return inten 
63   
64    def run(self, x = 0.0):
65        """
66        Evaluate the model
67       
68        param x: input q-value (float or [float, float] as [r, theta])
69        return: (scattering value)
70        """
71        if x.__class__.__name__ == 'list':
72            return self._corrlength(x[0])
73        elif x.__class__.__name__ == 'tuple':
74            raise ValueError, "Tuples are not allowed as input to BaseComponent models"
75        else:
76            return self._corrlength(x)
77   
78    def runXY(self, x = 0.0):
79        """
80        Evaluate the model
81       
82        param x: input q-value (float or [float, float] as [qx, qy])
83        return: scattering value
84        """
85        if x.__class__.__name__ == 'list':
86            q = math.sqrt(x[0]**2 + x[1]**2)
87            return self._corrlength(q)
88        elif x.__class__.__name__ == 'tuple':
89            raise ValueError, "Tuples are not allowed as input to BaseComponent models"
90        else:
91            return self._corrlength(x)
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