analysis.utils

The utils module provides a variety of general utility functions used across the analysis package.

Usage Example

from sndata.csp import dr3

from analysis import utils

# Convert dates from the Snoopy or MJD formats to JD format
dates = [350, 53350]  # snoopy and MJD respectively
jd_dates = utils.convert_to_jd(dates)
print(jd_dates)

# Get certain CSP data for a given target
t0 = utils.get_csp_t0(('2005kc'))
ebv = utils.get_csp_ebv(('2005kc'))

# Iterate over photometric data while only including targets with a published t0 and E(B-V)
for data in dr3.iter_data(filter_func=utils.filter_has_csp_data)

Function Documentation

analysis.utils.calc_model_chisq(data, result, model)

Calculate the chi-squared for a given data table and model

Chi-squared is calculated using parameter values from model. Degrees of freedom are calculated using the number of varied parameters specified is the result object.

Parameters:

• data (Table) – An sncosmo input table
• model (Model) – An sncosmo Model
• result (Result) – sncosmo fitting result

Returns:

The un-normalized chi-squared The number of data points used in the calculation

analysis.utils.filter_has_csp_data(data_table)

A filter function for an SNData table iterator

Returns whether the object ID associated with a data table has an available t0 and E(B - V) value.

Parameters:data_table (Table) – A table from sndata Returns:A boolean

analysis.utils.get_csp_ebv(obj_id)

Get the E(B - V) value published by CSP DR1 for a given object

Parameters:obj_id (str) – The object Id value Returns:The published E(B - V) value

analysis.utils.get_csp_t0(obj_id)

Get the t0 value published by CSP DR3 for a given object

Parameters:obj_id (str) – The object Id value Returns:The published date of maximum in JD format

analysis.utils.get_effective_wavelength(band_name)

Get the effective wavelength for a given band

Band name must be registered with SNCosmo.

Parameters:band_name (str) – The name of a registered bandpass Returns:The effective wavelength in Angstroms

analysis.utils.parse_spectra_table(data)

Convert spectral data from an astropy table to arrays

Parameters:data (Table) – A table of spectral data from sncosmo Returns:

• A sorted list of observed MJD dates for each spectra
• A 2d list of wavelength values for each date
• A 2d list of flux values for each date