synthesizer.load_data.utils

Utilities for data loading methods.

These utilities are used through the load_data module as helpers for loading data from different simulations sources.

Examples usage:

lengths = np.array([10, 20, 30]) begin, end = get_begin_end_pointers(lengths) print(begin) # Output: [ 0 10 30]

table = age_lookup_table(ages, redshift=0.5, delta_a=0.1) print(table) # Output: (array([0.1, 0.2, 0.3]), array([10., 20., 30.]))

ages = lookup_age(0.2, table[0], table[1])

Functions

synthesizer.load_data.utils.age_lookup_table(cosmo, redshift=0.0, delta_a=0.001, low_lim=0.0001)

Create a look-up table for age as a function of scale factor.

Defaults to start at the lower resolution limit (delta_a), and proceeds in steps of delta-a until the scale factor given by the input redshift minus the low_lim.

Parameters:

• cosmo (astropy.cosmology) – Astropy cosmology object.

• redshift (float) – Redshift of the snapshot.

• delta_a (int) – Scale factor resolution to approximate.

• low_lim (float) – Lower limit of scale factor.

Returns:

Array of scale factors. age (unyt_array of float):

Array of ages (Gyr).

Return type:

scale_factor (np.ndarray of float)

Examples using synthesizer.load_data.utils.age_lookup_table

Age lookup test

Age lookup test

synthesizer.load_data.utils.bin_overlap_matrix(lo, hi, grid_ages)

Fraction of each top-hat age bin falling in each grid age cell.

Cell edges follow parametric.Stars: zero, the linear midpoints between adjacent grid ages, then infinity so mass older than the grid is kept in the last cell. A zero-width bin is an instantaneous burst placed wholly in the cell containing its age.

Parameters:

• lo (np.ndarray of float) – Lower (younger) edge of each bin, in years.

• hi (np.ndarray of float) – Upper (older) edge of each bin, in years.

• grid_ages (np.ndarray of float) – Ascending grid ages, in years.

Returns:

(nbin, ngrid) overlap fractions.

Return type:

np.ndarray of float

synthesizer.load_data.utils.cast_component_dtype(component, dtype)

Cast floating-point arrays in component input data to one dtype.

Parameters:

• component (mapping or None) – Component constructor arguments from any data source.

• dtype (numpy dtype) – Target floating-point dtype.

Returns:

Shallow copy with floating-point arrays cast, preserving units.

Return type:

dict or None

synthesizer.load_data.utils.cic_matrix(values, grid)

Cloud-in-cell weights placing values on an ascending grid.

Values beyond the grid are clamped to the end points.

Parameters:

• values (np.ndarray of float) – The values to place (e.g. log10 metallicities).

• grid (np.ndarray of float) – Ascending grid coordinates.

Returns:

(nvalues, ngrid) weights, each row summing to 1.

Return type:

np.ndarray of float

synthesizer.load_data.utils.get_begin_end_pointers(length)

Find the beginning and ending indices from a length array.

Parameters:

length (np.ndarray of int) – The number of particles in each galaxy.

Returns:

Beginning indices. end (np.ndarray of int): Ending indices.

Return type:

begin (np.ndarray of int)

synthesizer.load_data.utils.lookup_age(scale_factor, scale_factors, ages)

Look up the age given a scale factor.

Parameters:

• scale_factor (np.ndarray of float) – Scale factors to convert to ages.

• scale_factors (np.ndarray of float) – Array of lookup scale factors.

• ages (unyt_array of float) – Array of lookup ages.

Returns:

Age based on the input scale factor/s.

Return type:

age (float)

Examples using synthesizer.load_data.utils.lookup_age

Age lookup test

Age lookup test

synthesizer.load_data.utils.split_age_bins(lo, hi, grid_ages)

Split top-hat age bins at every grid age they contain.

A bin narrower than the grid spacing is returned unchanged (one segment at its midpoint). Wider bins become one segment per grid age they straddle, so a constant SFR across the bin is resolved by the grid. A zero-width bin is an instantaneous burst: one segment at its age.

Parameters:

• lo (np.ndarray of float) – Lower (younger) edge of each bin, in years.

• hi (np.ndarray of float) – Upper (older) edge of each bin, in years.

• grid_ages (np.ndarray of float) – Ascending grid ages, in years.

Returns:

(bin index, midpoint age, width fraction) per segment.

Return type:

tuple