hats.pixel_math.sparse_histogram

Sparse 1-D histogram of healpix pixel counts.

Classes

SparseHistogram	Wrapper around a naive sparse array, that is just non-zero indexes and counts.
HistogramAggregator	Utility for aggregating sparse histograms.

Module Contents

class SparseHistogram(indexes, counts, order)

Wrapper around a naive sparse array, that is just non-zero indexes and counts.

e.g. for a dense 1-d numpy histogram of order 0, you might see:

[0, 4, 0, 0, 0, 0, 0, 0, 9, 0, 0]

There are only elements at [1, 8], and they have respective values [4, 9]. You would create the sparse histogram like:

SparseHistogram([1, 8], [4, 9], 0)

indexes

counts

order

to_array()

Convert the sparse array to a dense numpy array.

Returns:

np.ndarray

dense 1-d numpy array.

to_file(file_name)

Persist the sparse array to disk.

NB: this saves as a sparse array, and so will likely have lower space requirements than saving the corresponding dense 1-d numpy array.

Parameters:

file_namepath-like

intended file to save to

to_dense_file(file_name)

Persist the DENSE array to disk as a numpy array.

Parameters:

file_namepath-like

intended file to save to

classmethod from_file(file_name)

Read sparse histogram from a file.

Parameters:

file_namepath-like

intended file to save read from

Returns:

SparseHistogram

new sparse histogram

class HistogramAggregator(order)

Utility for aggregating sparse histograms.

order

full_histogram

add(other)

Add in another sparse histogram, updating this wrapper’s array.

Parameters:

otherSparseHistogram

the wrapper containing the addend

to_sparse()

Return a SparseHistogram, based on non-zero values in this aggregation.