add/subtract from existing column

[SpheMakh]

Add a feature that will add/subtract the predicted visibilities from an existing column

[KshitijT]

This feature would be really, really good to have - would save fiddling with msutils or worse, CASA. Would putting a tag of Mirto/Wine/Stroopwaffels (looking at you @sjperkins ) help?

[sjperkins]

Does anyone want to try use data column expressions that are in dask-ms master?

This test case illustrates their usage:

https://github.com/ska-sa/dask-ms/blob/master/daskms/tests/test_expression.py#L7-L28

[KshitijT]

Does anyone want to try use data column expressions that are in dask-ms master?

This test case illustrates their usage:

https://github.com/ska-sa/dask-ms/blob/master/daskms/tests/test_expression.py#L7-L28

Cool, let me try it out, will pester you if when I mess up.

[sjperkins]

Perfect, there's also a PR for tricolour here:

ratt-ru/tricolour#76

[sjperkins]

Which may provide insight

[sjperkins]

And docstrings here: https://github.com/ska-sa/dask-ms/blob/master/daskms/expressions.py#L54-L78