FitGauss.py File Reference

File containing methods for fitting Gaussian distributions to field components. More...

Functions
def	PyPO.FitGauss.calcEstimates (x, y, area, field_norm)
	Calculate estimates for beam parameters from an input field component. More...
def	PyPO.FitGauss.fitGaussAbs (field, surfaceObject, thres, scale, ratio=1)
	Fit a Gaussian to an amplitude pattern of a field component. More...
def	PyPO.FitGauss.GaussAbs (p0, *args)
	Generate absolute Gaussian from parameters. More...
def	PyPO.FitGauss.generateGauss (p0, surfaceObject, scale)
	Generate a Gaussian from Gaussian and surface parameters. More...

Detailed Description

File containing methods for fitting Gaussian distributions to field components.

Function Documentation

calcEstimates()

def PyPO.FitGauss.calcEstimates	(		x,
			y,
			area,
			field_norm
	)

Calculate estimates for beam parameters from an input field component.

These estimates are used as initial values for Gaussian fitting.

Parameters

x	Grid of x co-ordinates of input field.
y	Grid of y co-ordinates of input field.
area	Grid of area elements.
field_norm	Normalised input field component.

Returns

x0 Semi-major axis size of estimate.

y0 Semi-minor axis size of estimate.

xm Mean x-center of estimate.

ym Mean y-center of estimate.

theta Position angle of estimate.

fitGaussAbs()

def PyPO.FitGauss.fitGaussAbs	(		field,
			surfaceObject,
			thres,
			scale,
			ratio = 1
	)

Fit a Gaussian to an amplitude pattern of a field component.

First, the center and position angle of the pattern is calculated using the method of image moments. Then, local maxima that might interfere with fitting are removed using the findConnectedSubsets method from MatUtils.py.

Parameters

field	Component of field to fit.
surfaceObject	Surface on which the field is defined.
thres	Threshold for fitting in decibels.
mode	Whether to fit the Gaussian in linear or logarithmic space.
ratio	Allowed maximal ratio of fit to actual beam. If "None", will just attempt to fit the Gaussian to supplied pattern. If given, will only accept a fit if the ratio of integrated power in the fitted Gaussian to the supplied beam pattern is less than or equal to the given value. Defaults to 1.

Returns

popt Optimal parameters for Gaussian.

GaussAbs()

def PyPO.FitGauss.GaussAbs	(		p0,
		*	args
	)

Generate absolute Gaussian from parameters.

Called in optimalisation. This method returns an overlap parameter of the fitted Gaussian .

Parameters

p0	Array containing parameters for Gaussian.
args	Extra arguments for defining Gaussian and fit.

Returns

epsilon Coupling of field with Gaussian.

generateGauss()

def PyPO.FitGauss.generateGauss	(		p0,
			surfaceObject,
			scale
	)

Generate a Gaussian from Gaussian and surface parameters.

Parameters

p0	Gaussian parameters.
surfaceObject	Surface on which Gaussian is defined.
scale	Whether to generate Gaussian in linear or decibel space.

Returns

Psi Gaussian distribution.