Project/afw table/ishasan

[ih64]

this PR is for issue #51 , a guided tour to AFW tables in the basics section. Ready for comments and review :)

[ih64]

made changes suggested in stack club. Biggest changes:

1. commented on contiguous vs non contiguous tables. Demonstrating the difference by using %%timeit was not effective because the tables we are dealing with are too small for contiguity to make a difference. As a compromise, I include a link that shows an example using ~.5 million rows

2. I elected to remove the discussion of footprints and heavyfootprints. Going into a discussion of them would take us into a digression about source detection, and take away from the heart of the notebook, which is a guided tour to tables. I'm happy to do a separate footprint tutorial later.

3. I demonstrated catalog matching with two use cases. one where we keep only the nearest neighbors and one where we keep all matches within a search radius.

[drphilmarshall]

Hey @ih64 - apologies for the looong delay on reviewing this. I thought I remembered you saying you were thinking of extending this notebook a bit, but since I don't see any commits beyond the stack club group-review I guess that extension is on hold (or not planned) and the ball is still squarely in my court for reviewing/approving this. If I can get a good enough connection at Newark airport in tomorrow's club session I will do it then.

[drphilmarshall]

This is great, @ih64 - really nice work! I fixed a bunch of typos while working through your notebook, and will submit an easy PR against this branch with those. I then have just one final request - that we show how to make a table with ra and dec in degrees, not radians. I'll pre-approve though, so that you can merge whenever you've added that last feature. Thanks very much, this is going to be most useful!

[drphilmarshall]

Your example ra and dec look like they are in degrees, not radians - but I think it will be common for people to have coordinates in degrees. Perhaps this example should include showing what to do if this is indeed your situation. I guess the right thing to do is define the unit to be degrees when you instantiate the afwgeom.Angles? And then my last tiny suggestion is that your example dec should lie between 0 ad -70 deg :-)

[ih64]

Thanks @drphilmarshall! I now explicitly set the unit using keyword arguments when making afwGeom.Angles. Ready to merge (^^)/