The AstroStat Slog » Astrometry http://hea-www.harvard.edu/AstroStat/slog Weaving together Astronomy+Statistics+Computer Science+Engineering+Intrumentation, far beyond the growing borders Fri, 09 Sep 2011 17:05:33 +0000 en-US hourly 1 http://wordpress.org/?v=3.4 my first AAS. I. Regression http://hea-www.harvard.edu/AstroStat/slog/2008/firstaas-regression/ http://hea-www.harvard.edu/AstroStat/slog/2008/firstaas-regression/#comments Mon, 09 Jun 2008 00:38:27 +0000 hlee http://hea-www.harvard.edu/AstroStat/slog/?p=330 My first impression from the 212th AAS meeting is that it’s planned for preparing IYA 2009 and many talks are about current and future project reviews and strategies to reach public (People kept saying to me that winter meetings are more grand with expanded topics). I cannot say I understand everything (If someone says no astronomers understand everything, I’ll be relieved) but thanks to the theme of the meeting, I was intelligently entertained enough in many respects. The downside of this intellectual stimulus is growing doubts. One of those doubts was regression analysis in astronomy.

I’m not going to name the session, the speaker, nor the topic. Only relevant story related to regression analysis.

One of sessions, a speaker showed a slide with a headline, … test Ho…. My expectation was that Ho indicated a null hypothesis related to the expansion of the universe so that he was going to do a hypothesis testing. I was wrong. This Ho was the Hubble constant and his plan was estimating it with his carefully executed astrometry.

After a few slides later, I saw a straight line overplotted on top of scattered points. If I dissect the given space into 4×4, the most of points were occupied in the lower left corner section, and there was only one point placed in the section of the upper right corner. This single point had the most leverage that determines the slope of the line. Without verification, such as using Cook’s distance, I wondered what would happen with the estimated slope. Even with that high leverage point, I wondered if he still could claim with real statistics that his slope (Ho) estimate prefers the model by Freedman to the model by Sandage? To my naive eyes, the differences between the estimated slope from data and the two theoretical slopes are hardly distinguishable.

I saw papers in astronomy/astrophysics that carefully explain caveats of regression analysis on their target data and describe statistical tests to show the differences and similarities. Probably, the speaker didn’t want to disturb the audience with boring statistics. Yet, this was one of the occasions where my doubts toward astronomers who practice statistics in their own ways without consulting scholarly works in statistics sufficiently. The other likelihood is that I myself is biased to see things. I bet I’m the only one who expected that …test Ho… would accompany a null hypothesis and hypothesis tests, instead of estimating the Hubble constant.

]]> http://hea-www.harvard.edu/AstroStat/slog/2008/firstaas-regression/feed/ 0 Astrometry.net http://hea-www.harvard.edu/AstroStat/slog/2008/astrometrynet/ http://hea-www.harvard.edu/AstroStat/slog/2008/astrometrynet/#comments Wed, 12 Mar 2008 19:32:49 +0000 hlee http://hea-www.harvard.edu/AstroStat/slog/2008/astrometrynet/ Astrometry.net, a cool website I heard from Harvard Astronomy Professor Doug Finkbeiner’s class (Principles of Astronomical Measurements), does a complex job of matching your images of unknown locations or coordinates to sources in catalogs. By providing your images in various formats, they provide astrometric calibration meta-data and lists of known objects falling inside the field of view.

Astrometry is a branch of astronomy but the algorithms of locating stars and galaxies mainly come from computer scientists whose fundamental ideas are from statistics and mathematics.

]]> http://hea-www.harvard.edu/AstroStat/slog/2008/astrometrynet/feed/ 0 [ArXiv] 4th week, Oct. 2007 http://hea-www.harvard.edu/AstroStat/slog/2007/arxiv-4th-week-oct-2007/ http://hea-www.harvard.edu/AstroStat/slog/2007/arxiv-4th-week-oct-2007/#comments Fri, 26 Oct 2007 22:52:02 +0000 hlee http://hea-www.harvard.edu/AstroStat/slog/2007/arxiv-4th-week-oct-2007/ I hope there are a paper or two drags your attentions and stimulates your thoughts in astrostatistics from arXiv.

  • [stat.ML:0710.3742]
    Bayesian Online Change Point Detection by R. Adams and D. MacKay
  • [astro-ph:0710.3600]
    Statistical Methods for Investigating the Cosmic Ray Energy Spectrum by J. Hague, B. Becker, M. Gold, J.Matthews, and J. Urb\’a\v{r}
  • [astro-ph:0710.3618]
    Fast algorithms for matching CCD images to a stellar catalogue by V. Tabur
  • [astro-ph:0710.4019]
    A principal component analysis approach to the morphology of Plaetary Nebulae by S. Akras and P. Boumis
  • [astro-ph:0710.4020]
    Dice and Pulsars by V. M. Kontorovich
  • [astro-ph:0710.4075]
    Getting More From Your Multicore: Exploiting OpenMP for Astronomy by M. S. Noble
  • [astro-ph:0710.4143]
    Lensing and Supernovae: Quantifying The Bias on the Dark Energy Equation of State by D. Sarkar and A. Amblard
  • [astro-ph:0710.4158]
    A Cross-Match of 2MASS and SDSS: Newly-Found L and T Dwarfs and an Estimate of the Space Density of T Dwarfs by S. Metchev, et. al.
  • [astro-ph:0710.4262]
    Crowded-Field Astrometry with the Space Interferometry Mission – I. Estimating the Single-Measurement Astrometric Bias Arising from Confusion by R. Sridharan and R. Allen
  • [astro-ph:0710.4556]
    X-Ray Binaries and the Current Dynamical States of Galactic Globular Clusters by J. M. Fregeau
  • [stat.ME]
    The Use of Unlabeled Data in Predictive Modeling by F. Liang, S. Mukherjee, and M. West
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