Source code for sas.models.PeakLorentzModel

#!/usr/bin/env python
""" 
    Model describes a Lorentzian shaped peak including a flat background
    Provide F(q) = scale/(1+[(q-q0)/B]^2 ) + background
    PeakLorentzModel function as a BaseComponent model
"""

from sas.models.BaseComponent import BaseComponent
import math

[docs]class PeakLorentzModel(BaseComponent): """ Class that evaluates a gaussian shaped peak. F(q) = scale/(1+[(q-q0)/B]^2 ) + background The model has three parameters: scale = scale q0 = peak position B = ( hwhm) half-width-halfmaximum background= incoherent background """ def __init__(self): """ Initialization """ # Initialize BaseComponent first, then sphere BaseComponent.__init__(self) ## Name of the model self.name = "Peak Lorentz Model" self.description = """ F(q) = scale/(1+[(q-q0)/B]^2 ) + background The model has three parameters: scale = scale q0 = peak position B = ( hwhm) half-width-halfmaximum background= incoherent background""" ## Define parameters self.params = {} self.params['scale'] = 100.0 self.params['q0'] = 0.05 self.params['B'] = 0.005 self.params['background'] = 1.0 ## Parameter details [units, min, max] self.details = {} self.details['q0'] = ['[1/A]', None, None] self.details['scale'] = ['', 0, None] self.details['B'] = ['[1/A]', None, None] self.details['background'] = ['[1/cm]', None, None] #list of parameter that cannot be fitted self.fixed = [] def _PeakLorentz(self, x): """ Evaluate F(x) = scale/(1+[(x-q0)/B]^2 ) + background """ return self.params['scale']/(1+\ math.pow((x - self.params['q0'])/self.params['B'],2)) \ + self.params['background']
[docs] def run(self, x = 0.0): """ Evaluate the model @param x: input q-value (float or [float, float] as [r, theta]) @return: Peak Lorentzian value """ if x.__class__.__name__ == 'list': return self._PeakLorentz(x[0]) elif x.__class__.__name__ == 'tuple': raise ValueError, "Tuples are not allowed as input to BaseComponent models" else: return self._PeakLorentz(x)
[docs] def runXY(self, x = 0.0): """ Evaluate the model @param x: input q-value (float or [float, float] as [qx, qy]) @return: Peak Lorentzian value """ if x.__class__.__name__ == 'list': q = math.sqrt(x[0]**2 + x[1]**2) return self._PeakLorentz(q) elif x.__class__.__name__ == 'tuple': raise ValueError, "Tuples are not allowed as input to BaseComponent models" else: return self._PeakLorentz(x)