BayesicFitting

Model Fitting and Evidence Calculation

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class PowerModel( LinearModel )Source

General power model of arbitrary degree.

     f( x:p ) = p * xa

a is an float ( positive or negative ).

To get the overall units of f(x:p) right, please note that the x-term needs to be divided by a factor 1.0 in the same units as the x. Otherwise possibly fractional dimensions are created. The factor is omitted as it does not contribute in the calculations.

Examples

pwr = PowerModel( -1 )
print pwr.getNumberOfParameters( )       # 1
1

Attributes

  • exponent : float
         exponent (a) of the power function.

Attributes from Model

     npchain, parameters, stdevs, xUnit, yUnit

Attributes from FixedModel

     npmax, fixed, parlist, mlist

Attributes from BaseModel

     npbase, ndim, priors, posIndex, nonZero, tiny, deltaP, parNames

PowerModel( exponent=0, copy=None, **kwargs )

Power of a certain degree.

The number of parameters is 1

Parameters

  • exponent : int
         power to which the xdata is to be raised.
  • copy : PowerModel
         to be copied
  • fixed : None or dictionary of {int:float|Model}
         int index of parameter to fix permanently.
         float|Model values for the fixed parameters.
         Attribute fixed can only be set in the constructor.
         See: FixedModel

copy( )

Copy method.

basePartial( xdata, params, parlist=None )
Returns the partials at the xdata value.
The partials are x ( xdata ) to degree-th power.

Parameters

  • xdata : array_like
         values at which to calculate the result
  • params : array_like
         values for the parameters. (not used for linear models)
  • parlist : array_like
         list of indices active parameters (or None for all)

baseDerivative( xdata, params )
Return the derivative df/dx at each xdata (=x).

Parameters

  • xdata : array_like
         values at which to calculate the result
  • params : array_like
         values for the parameters.

baseName( )
Returns a string representation of the model.

baseParameterUnit( k )
Return the name of a parameter. Not strictly OK. See Class documentation. Parameters
  • k : int
         the kth parameter.
Methods inherited from LinearModel
Methods inherited from Model
Methods inherited from FixedModel
Methods inherited from BaseModel