[lsst-dm-stack-users] How to calculate RMS, sigma-clipped RMS on DM Winter2013 Stripe82 forced photometry

[Michael Wood-Vasey]

Hi Simon,

See you tomorrow (Thursday).  I think my list of statistics that I would like to see is:

1. RMS
2. chisq 
3. clipped mean  (5-sigma)
4. RMS from clipped mean
5. chisq from clipped mean

I took a look through Bramich et al. 2008 (http://labs.adsabs.harvard.edu/ui/abs/2008MNRAS.386..887B) and this covers most of them (the used a 4-sigma clipped mean, I'm not quite sure why 4).  There are also a few measures suggested by Stetson in Stetson 1996 (http://labs.adsabs.harvard.edu/ui/abs/1996PASP..108..851S), as well as the Vidrih index (which if I understand correctly can be calculated based on the other statistics above).

Abi Saha just sat down next to me and suggested that a general exploration of moments and some interesting combinations of moments can be interesting.  I think this is something to consider for future, but not necessarily immediately.  For now I would be interested in the first 5 above.

Thanks,
Michael

On Jan 9, 2013, at 20:19 , Simon Krughoff <simon.krughoff at gmail.com> wrote:

> Sounds good.  I'm at SLAC already, so just track me down when you want to chat.
> 
> Simon
> 
> P.S. Of course, you are right that we calculated the median not the mean.  Sorry for the mistype.
> 
> On Wed, Jan 9, 2013 at 2:00 PM, Michael Wood-Vasey <wmwv at pitt.edu> wrote:
> On Jan 9, 2013, at 09:22 , Simon Krughoff <simon.krughoff at gmail.com> wrote:
> > To follow up with this, as you know we have already calculated the mean and inner quartile range for all the lightcurves in the database.
> 
> Yes (although it's actually the median not the mean).
> 
> >  We are planning on adding a clipped mean and standard deviation within the next week or so.  It's possible that all you'll have to do is wait.  If there are other quantities you'd like materialized, we can potentially add those as well.
> 
> That would be perfect.  Let me try to come up with what this list should be by later this week and we can talk at the DESC meeting.
> 
>  - Michael
> 
> 
> 
> 
> -- 
> K. Simon Krughoff
> University of Washington
> Department of Astronomy
> 
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