The AstroStat Slog

From arXiv/astro-ph:0706.4484

Spectroscopic Surveys: Present by Yip. C. overviews recent spectroscopic sky surveys and spectral analysis techniques toward Virtual Observatories (VO). In addition that spectroscopic redshift measures increase like Moore’s law, the surveys tend to go deeper and aim completeness. Mainly elliptical galaxy formation has been studied due to more abundance compared to spirals and the galactic bimodality in color-color or color-magnitude diagrams is the result of the gas-rich mergers by blue mergers forming the red sequence. Principal component analysis has incorporated ratios of emission line-strengths for classifying Type-II AGN and star forming galaxies. Lyα identifies high z quasars and other spectral patterns over z reveal the history of the early universe and the characteristics of quasars. Also, the recent discovery of 10 satellites to the Milky Way is mentioned.
Continue reading ‘[ArXiv] Spectroscopic Survey, June 29, 2007’ »

From arXiv:physics.data-an/0706.3622v1:
Comments on the unified approach to the construction of classical confidence intervals

This paper comments on classical confidence intervals and upper limits, as the so-called a flip-flopping problem, both of which are related asymptotically (when n is large enough) by the definition but cannot be converted from one to the another by preserving the same coverage due to the poisson nature of the data.
Continue reading ‘[ArXiv] Classical confidence intervals, June 25, 2007’ »

One of the papers from arxiv/astro-ph discusses kernel regression and model selection to determine photometric redshifts astro-ph/0706.2704. This paper presents their studies on choosing bandwidth of kernels via 10 fold cross-validation, choosing appropriate models from various combination of input parameters through estimating root mean square error and AIC, and evaluating their kernel regression to other regression and classification methods with root mean square errors from literature survey. They made a conclusion of flexibility in kernel regression particularly for data at high z.
Continue reading ‘[ArXiv] Kernel Regression, June 20, 2007’ »

From arxiv/astro-ph, arXiv:0706.2590v1 Extreme Value Theory and the Solar Cycle by Ramos, A. This paper might drag a large attention from CHASC members.
Continue reading ‘[ArXiv] Solar Cycle, June 18, 2007’ »

One of arxiv/astro-ph preprints, arxiv/0706.1703v1 discusses correlation between galactic HI and the cosmic microwave background (CMB) and reports no statistically significant correlation.
Continue reading ‘[ArXiv] Correlation Studies, June 12, 2007’ »

From arxiv/astro-ph:0706.1988,
Lectures on Astronomy, Astrophysics, and Cosmology looks helpful to statisticians who like to know astronomy, astrophysics, and cosmology. The lecture note starts from introducing fundamentals of astronomy, UNITS!!!, and its history. It also explains astronomical measures such as distances and their units, luminosity, and temperature; HR diagram (astronomers’ summary diagram); stellar evolution; and relevant topics in cosmology. At least, a third of the article will be useful to grasp a rough idea of astronomy as a scientific subject beyond colorful pictures. Statisticians who are keen to cosmology are recommended to read beyond.

This is not a high energy lecture note; therefore, statisticians interested in high energy are encouraged to visit Astro Jargon for Statisticians and CHASC.

Terry Speed writes columns for IMS Bulletin and the June 2007 issue has Terence’s Stuff: Data Doctors (p. 7). He quotes Fisher who described a statistician as a post-mortem examiner or a pathologist, but thinks that statisticians (statistical consultants) are doctors who maintain close, active, and alive relationships with their patients.

Nonetheless, I think statisticians working with astronomers are assistants to post-mortem examiners. Most likely, statisticians nor astronomers cannot design experiments with unreachable objects. Astronomers are post-mortem examiners with telescopes and statisticians are assistants with charts which are by products from post-mortem examinations. These assistants may or may not be useful to astronomers.

A Link to Statistical Analysis for the Virtual Observatory is added. Its description with toy data is given at
http://www.astrostatistics.psu.edu/vostat/.

Nice feature of this website is that the interface allows you to perform various statistical analysis on a data set which is located either at your hard disk or at the Virtual Observatory.

GLAST workshop will be held at Science Center (Hall A, located at the 1st floor) of Harvard University. Nice opportunity to learn about GLAST mission and its programs. Free registration and open to everyone. Please, visit
http://glast.gsfc.nasa.gov/workshops/boston/ for registration and further information.

John Rice is visiting IIC. The meeting and his talk is scheduled on Friday, June 8, at 11:30am (room 403 at 60 Oxford St.).

Title: Event Weighted Tests for Periodicity in a Sequence of Photon Arrival Times:
Detecting Gamma-ray Pulsars.

[Added] Another meeting is scheduled at the stat dept. located in Science Center, 4-6pm, Wednesday (June 6th).

Leo Breiman (1928-2005) was one of the most dominant statisticians from the 20th century. He was well known for his textbook in probability theory as well as his contributions to the machine learning, such as CART (Classification and Regression Tree), bagging (bootstrap aggregation), and Random Forest. He was the founding father of statistical machine learning. His works can be found from http://www.stat.berkeley.edu/~breiman/

An excerpt from “A Conversation with Leo Breiman,” from Statistical Science, by Richard Olshen (2001), 16(2), pp. 184–198, casts a second thought on the direction of statistical researches:
Continue reading ‘An excerpt from “A Conversation with Leo Breiman”’ »

R is a programming language and software for statistical computing and graphics. It is the most popular tool for statisticians and a widely used software for statistical data analysis thanks to the fact that its source code is freely available and it is fairly easy to access from installation to theoretical application.

Most of information about R can be found at R Project including the software itself and many add-on packages. These individually contributed packages serve particular statistical interests of their users. The documentation menu on the website and each packages contain extensive documentations of how-to’s. Some large packages include demos so that following the scripts in a demo makes R learning easy.
Continue reading ‘Learning R’ »

The Statistics Jargon for Astronomers has revived (Jan. 2007) but now, it is barely breathing. Effortlessly search engines and Internet encyclopedia provide details on statistical terminologies for astronomers, which cast the largest difficulty on this jargon website. We urge both astronomers and statisticians’ contributions for compiling this lexicon and their discussions on both subjects.

In Spring 2006, SAMSI (Statistical and Applied Mathematical Sciences Institute) program on Astrostatistics began with tutorials, followed by workshops and regular meetings of working groups (Exoplanets, Surveys and Population Studies, Gravitational Lensing, Source Detection and Feature Detection, Particle Physics). Workshop speakers/participants and working group members brought up many statistical challenges in astronomy and physics and had extensive discussions. Summaries and relevant materials are available from the websites (click the links; some materials such as journal papers are password protected).

Since Summer 2005, G. Jogesh Babu (Statistics) and Eric Feigelson (Astronomy) have organized lectures and lab sessions on statistics for astronomers and physicists. Lecturers are professors from Penn State statistics department and invited renown scientists from different countries. Students show diverse demography as well. Within a week or so, students listen Statistics 101 to recently published statistical theories particularly applied to astronomical data. They also learn how to use R, a statistical software and script language to perform statistics they learn through lectures. Past two years, this summer school proved its uniqueness and usefulness. More information on the upcoming school can be found at http://astrostatistics.psu.edu/su07/index.html and other topics regarding astrostatistics at Center for AstroStatistics at Penn State.