Data Column Expressions

[sjperkins]

• [x] Tests added / passed

  $ py.test -v -s daskms/tests

  If the pep8 tests fail, the quickest way to correct this is to run autopep8 and then flake8 and pycodestyle to fix the remaining issues.

  $ pip install -U autopep8 flake8 pycodestyle
  $ autopep8 -r -i daskms
  $ flake8 daskms
  $ pycodestyle daskms

• [x] Fully documented, including HISTORY.rst for all changes and one of the docs/*-api.rst files for new API

  To build the docs locally:

  pip install -r requirements.readthedocs.txt
  cd docs
  READTHEDOCS=True make html

[sjperkins]

@o-smirnov @bennahugo @IanHeywood @JSKenyon @smasoka @rubyvanrooyen

Primarily with https://github.com/ska-sa/tricolour/issues/70 in mind but might be useful elsewhere:

Code snippet:

datasets = xds_from_ms("WSRT.MS")
datasets = data_column_expr("2 * DATA / (DIR1_DATA + DIR2_DATA)", datasets)
consume(datasets[0].DATA_EXPRESSION.data)

[sjperkins]

and @landmanbester of course

[sjperkins]

Changed to support assignments:

datasets = xds_from_ms("WSRT.MS")
datasets = data_column_expr("EXPR = 2 * DATA / (DIR1_DATA + DIR2_DATA)", datasets)
consume(datasets[0].EXPR.data)

[o-smirnov]

This is an absolutely awesome change, much more powerful than my simple binary arithmetic. I look forward to supporting this in shadeMS!

[sjperkins]

It supports a simple calculator syntax at the moment (no functions), but it could always be expanded later.

[sjperkins]

OK this is percolating in master if people wish to try it out. I've also exposed the docstrings on readthedocs.io