ccfcenter Namespace Reference

This module finds the center and width of a MARVELS ccf. More...

Functions
def	cutccf
	Choose which section of the ccf to fit based on width parameter or automatically using percent.
def	gaussfunc
	Takes x points and returns a Gaussian function.
def	gausstest
	Creates a Gaussian signal and then fits it to see if I can recover the input parameters.
def	fitgauss
	Use a Levenberg-Marquadt non-linear least-squares fitter to fit a Gaussian to Xin and Yin.
def	make_gauss
	Generate Gaussian data using Gaussian.
def	ccfcenter
	This function is the main() program for this module.
Variables
list	filename = sys.argv[1]
	width = None
tuple	ret = ccfcenter(filename,width)

---

Detailed Description

This module finds the center and width of a MARVELS ccf.

This module uses a non-linear least-squares optimizer from scipy to fit a Gaussian to the central pixels of a ccf file.

Author:

Nathan De Lee

Version:

Revision:

1.2

Date:

Date:

2012-01-13 20:12:24

---

Function Documentation

def ccfcenter::ccfcenter	(		filename,
			width = None
	)

This function is the main() program for this module.

Parameters:

filename	String name of MARVELS ccf file to process
width	Integer number of pixels to fit around peak; None: Automatically choose

Returns:

The function returns 0 for success or an error message.

Return values:

ret	0 for success or an error message

Definition at line 247 of file ccfcenter.py.

def ccfcenter::cutccf	(		pixel,
			ccf,
			width = None,
			percent = 0.30
	)

Choose which section of the ccf to fit based on width parameter or automatically using percent.

Parameters:

pixel	Numpy array of pixel positions
ccf	Numpy array of ccf values
width	Integer number of pixels to include, if None: then automatically determine.
percent	Floating point percentage of the singal amplitude above the noise that a point must be to be included in the fit.

Returns:

This function returns a tuple (pixel,ccf,lmargin,rmargin ,noiselevel).

Return values:

pixel	Numpy array of pixel positions
ccf	Numpy array of ccf values
lmargin	Integer index of the left margin of the input arrays
rmargin	Integer index of the right margin of the input arrays
noiselevel	Floating point values of the CCF plot noise level

Definition at line 52 of file ccfcenter.py.

def ccfcenter::fitgauss	(		xin,
			yin,
			inerror = [],
			inguess = [1
	)

Use a Levenberg-Marquadt non-linear least-squares fitter to fit a Gaussian to Xin and Yin.

The scipy module optimize is used to find the smallest residual to Error Function which is compared to the Gaussian function.

Parameters:

xin	Numpy array of x-values
yin	Numpy array of y-values
inerror	Numpy array of error values
inguess	A 3 element list (Amplitude,Offset,Sigma) of starting values for Gaussian parameters

Returns:

This function returns a tuple (Params, perror , red_chi)

Return values:

Params	A 3 element Numpy array of Gaussian Parameters (Amplitude,Offset,Sigma)
perror	A 3 element Numpy array of parameter errors calculated from the covariance matrix
red_chi	A float giving the reduced \(\chi^{2}\) of the fit.

Remarks:

If there are no measurement errors then the parameter errors must be scaled by the reduced chisq Section 15.2 in Numerical Recipes discusses this.

Definition at line 151 of file ccfcenter.py.

def ccfcenter::gaussfunc	(		P,
			x
	)

Takes x points and returns a Gaussian function.

Parameters:

P	A 3 element array (Amplitude,Offset,Sigma)
x	Numpy array of x positions

Returns:

y values for the x positions and parameters given

Return values:

y	Numpy array of y values

Definition at line 77 of file ccfcenter.py.

def ccfcenter::gausstest

(

)

Creates a Gaussian signal and then fits it to see if I can recover the input parameters.

Returns:

None

Todo:

Make a histogram of all the parameters

Definition at line 95 of file ccfcenter.py.

def ccfcenter::make_gauss	(		npts,
			amp = 1,
			offset = 0,
			sigma = 1,
			error = 0,
			inflate_error = 1.0,
			randpts = False
	)

Generate Gaussian data using Gaussian.

Parameters:

npts	Integer number of points to create
amp	Floating point amplitude of the Gaussian
offset	Floating point offset of the Gaussian
sigma	Floating point sigma of the Gaussian
error	Floating point number or a Numpy array of sigmas for the error in each point
inflate_error	Floating point factor to scale the real as versus reported error
randpts	Bool True: Select x points from a uniform distribution; False Take from a regular grid.

Returns:

This function returns a tuple (x,y,y_err)

Return values:

x	Numpy Array of x positions
y	Numpy Array of y positions
y_err	Numpy Array of y errors

Definition at line 220 of file ccfcenter.py.

---

Variable Documentation

list ccfcenter::filename = sys.argv[1]

Definition at line 328 of file ccfcenter.py.

tuple ccfcenter::ret = ccfcenter(filename,width)

Definition at line 334 of file ccfcenter.py.

ccfcenter::width = None

Definition at line 333 of file ccfcenter.py.