imcascade.utils

Module Contents

Functions

guess_weights(sig, re, flux)

Method to guess the weights of gaussian componenets given an re and flux.

expand_mask(mask[, radius, threshold])

Expands mask by convolving it with a Gaussians

asinh_scale(start, end, num)

Simple wrapper to generate list of numbers equally spaced in asinh space

log_scale(start, end, num)

Simple wrapper to generate list of numbers equally spaced in logspace

dict_add(dict_use, key, obj)

Simple wrapper to add obj to dictionary if it doesn’t exist. Used in fitter.Fitter when defining defaults

get_med_errors(arr[, lo, hi])

Simple function to find percentiles from distribution

b(n)

Simple function to approximate b(n) when evaluating a Sersic profile

sersic(r, n, re, Ltot)

Calculates the surface brightness profile for a Sersic profile

min_diff_array(arr)

Function used to calculate the minimum difference between any two elements

Attributes

vars_to_use

imcascade.utils.vars_to_use = ['img', 'weight', 'mask', 'sig', 'Ndof', 'Ndof_sky', 'Ndof_gauss', 'has_psf', 'psf_a',...
imcascade.utils.guess_weights(sig, re, flux)

Method to guess the weights of gaussian componenets given an re and flux. Based on a polynomial fit to the exp fits of Hogg & Lang 2013

Parameters

  • sig (array) – List of gaussian widths for imcascade model

  • re (Float) – Estimate of effective radius

  • flux – Estimate of flux

Returns

a_i – Inital estimate of weights based on re and flux

Return type

Array

imcascade.utils.expand_mask(mask, radius=5, threshold=0.001)

Expands mask by convolving it with a Gaussians

Parameters

  • Mask (2D array) – inital mask with masked pixels equal to 1

  • radius (Float) – width of gaussian used to convolve mask. default 5, set larger for more aggresive masking

  • threshold (Float) – threshold to generate new mask from convolved mask. Default is 1e-3, set lower for more aggresive mask

Returns

new_mask – New, expanded mask

Return type

2D-Array

imcascade.utils.asinh_scale(start, end, num)

Simple wrapper to generate list of numbers equally spaced in asinh space

Parameters

  • start (floar) – Inital number

  • end (Float) – Final number

  • num (Float) – Number of number in the list

Returns

list – List of number spanning start to end, equally space in asinh space

Return type

1d array

imcascade.utils.log_scale(start, end, num)

Simple wrapper to generate list of numbers equally spaced in logspace

Parameters

  • start (floar) – Inital number

  • end (Float) – Final number

  • num (Float) – Number of number in the list

Returns

list – List of number spanning start to end, equally space in log space

Return type

1d array

imcascade.utils.dict_add(dict_use, key, obj)

Simple wrapper to add obj to dictionary if it doesn’t exist. Used in fitter.Fitter when defining defaults

Parameters

  • dict_use (Dictionary) – dictionary to be, possibly, updated

  • key (str) – key to update, only updated if the key doesn’t exist in dict_use already

  • obj (Object) – Object to be added to dict_use under key

Returns

dict_add – updated dictionary

Return type

Dictionary

imcascade.utils.get_med_errors(arr, lo=16, hi=84)

Simple function to find percentiles from distribution

Parameters

  • arr (array) – Array containing in the distribution of intrest

  • lo (float (optional)) – percentile to define lower error bar, Default 16

  • hi (float (optional)) – percentile to define upper error bar, Default 84

Returns

(med,err_lo,err_hi) – Array containg the median and errorbars of the distiribution

Return type

array

imcascade.utils.b(n)

Simple function to approximate b(n) when evaluating a Sersic profile following Capaccioli (1989). Valid for 0.5 < n < 10

Parameters

n (float or array) – Sersic index

Returns

b(n) – Approximation to Gamma(2n) = 2 gamma(2n,b(n))

Return type

float or array

imcascade.utils.sersic(r, n, re, Ltot)

Calculates the surface brightness profile for a Sersic profile

Parameters

  • r (array) – Radii at which to evaluate surface brightness profile

  • n (float) – Sersic index of profile

  • re (float) – Half-light radius of profile

  • Ltot (float) – Total flux of Sersic profile

Returns

Surface brightness profile evaluate along the semi-major axis at ‘r’

Return type

float or array

imcascade.utils.min_diff_array(arr)

Function used to calculate the minimum difference between any two elements in a given array_like :param arr: Array to be searched :type arr: 1-D array

Returns

min_diff – The minimum difference between any two elements of the given array

Return type

Float