Comparing and contrasting datasets
Often people are quite confused about the differences between flagging values in SDSS data. Here's how you can get a quick look at it.
Example: looking at the impact of flagging columns#
Let's create three subsets. Both on the ASPCAP
dataset, but with three differences in flagging.
- No filtering at all
flag_bad == 0
result_flags == 0
Note
You must disable the default purely non flagged
option in the Quick Flags, under the Targeting Filters menu.
The setup described above. Use the Expression field to setup the flagging checks.
Now create 3 heatmaps, plotting teff
vs logg
and set the bintype to count
with a logscale. Make sure to flip the axes, and set the Subset in each to the correct one.
The setup described above. Top left: no filtering. Top right: flag bad == 0. Bottom: result_flags == 0. Look at the structural differences.