xarray-kat 0.0.1

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This package present an xarray view over observations in the MeerKAT archive.

Required Reading

You’ll need some familiarity with xarray. In particular:

• Indexing and selecting data

• Lazy Loading behaviour

Example Usage

At a basic level, one can use xarray’s selection and lazy loading mechanisms to interact with the data:

import xarray_kat
import xarray

token = "eyFILLMEIN"
capture_block_id = 123456789
url = f"https://archive-gw-1.kat.ac.za/{capture_block_id}/{capture_block_id}_sdp_l0.full.rdb?token={token}"

# If the dataset is small you may be able to load it all in at once
dt = xarray.open_datatree(url, chunked_array_type="xarray-kat", chunks={})
dt.load()

# Otherwise one can select a small partition of the data
# that can fit in memory and interact with that
ds = dt["123456789_sdp_l0"].ds
ds = ds.isel(time=slice(10, 20), baseline_id=[1, 20, 30, 31, 32, 50], frequency=slice(256, 768))
ds.load()

If dask is installed, one can request chunking along dimensions:

import xarray_kat
import xarray

token = "eyFILLMEIN"
capture_block_id = 123456789
url = f"https://archive-gw-1.kat.ac.za/{capture_block_id}/{capture_block_id}_sdp_l0.full.rdb?token={token}"

# This specifies the natural chunking of the
# underlying store
dt = xarray.open_datatree(url, chunks={})
dt = dt.compute()

# More exotic chunking can be selected, but
# as this pattern does not match the natural
# chunking, it results in repeated requests for
# the same data. It may be better to use a
# dask.rechunk operation ontop of the natural
# chunking, or use cache pools to ameliorate this
dt = xarray.open_datatree(url, chunks={"time": 20, "baseline_id": 155, "frequency": 256})
dt = dt.compute()