Apr 30th, 2010| 12:12 pm | Posted by vlk

Sherpa is a fitting environment in which Chandra data (and really, X-ray data from any observatory) can be analyzed. It has just undergone a major update and now runs on python. Or allows python to run. Something like that. It is a very powerful tool, but I can never remember how to use it, and I have an amazing knack for not finding what I need in the documentation. So here is a little cheat sheet (which I will keep updating ~~as and when~~ if I learn more): Continue reading ‘Everybody needs crampons’ »

Tags:

Chandra,

cheat sheet,

ciao,

how to,

Python,

Sherpa,

Sherpa4 Category:

Algorithms,

Astro,

Fitting,

Jargon,

Languages |

2 Comments
Nov 13th, 2009| 04:46 pm | Posted by hlee

I was told to stay away from python and I’ve obeyed the order sincerely. However, I collected the following stuffs several months back at the instance of hearing about import inference and I hate to see them getting obsolete. At that time, collecting these modules and getting through them could help me complete the first step toward the quest Learning Python (the first posting of this slog). Continue reading ‘some python modules’ »

Tags:

APLpy,

AstroPy,

IDLsave,

import inference,

libraries,

modules,

package,

Pyfits,

PyMC,

PyRAF,

PYSTAT,

Python,

PyWavelets Category:

Algorithms,

Astro,

Cross-Cultural,

Data Processing,

Jargon,

Languages,

Methods,

News,

Stat |

2 Comments
Jul 30th, 2009| 01:57 am | Posted by hlee

##### X={ primer, tutorial, cookbook, Introduction, guidebook, 101, for dummies, …}

#####

I’ve heard many times about ** the lack of documentation** of this extensive data analysis system, **ciao**. I saw people still using ciao 3.4 although the new version 4 has been available for many months. Although **ciao** is not the only tool for Chandra data analysis, it was specifically designed for it. Therefore, I expect it being used frequently with popularity. But the reality is against my expectation. Whatever (fierce) discussion I’ve heard, it has been irrelevant to me because **ciao** is not intended for statistical analysis. Then, out of sudden, after many months, a realization hit me. **ciao is different from other data analysis systems and softwares.** This difference has been a hampering factor of introducing ciao outside the Chandra scientist community and of gaining popularity. This difference was the reason I often got lost in finding suitable documentations. Continue reading ‘Where is ciao X ?’ »

Tags:

ciao,

cookbook,

documentation,

guide,

introduction,

matlab,

primer,

Python,

R,

SAS,

software,

Tutorial Category:

Cross-Cultural,

Languages,

Misc |

1 Comment
May 7th, 2009| 02:22 pm | Posted by hlee

Almost 100 years ago, A.S. Eddington stated in his book *Stellar Movements* (1914) that

…in calculating the mean error of a series of observations it is preferable to use the simple mean residual irrespective of sign rather than the mean square residual

Such eminent astronomer said already *least absolute deviation* over *chi-square*, if I match *simple mean residual* and *mean square residual* to relevant methodologies, in order. Continue reading ‘a century ago’ »

Tags:

chi-square minimization,

Eddington,

inference,

LAD,

Laplace,

mse,

PyMC,

Python,

R.A.Fisher,

utility function Category:

Astro,

Cross-Cultural,

Quotes,

Stat,

Uncertainty |

Comment
Sep 16th, 2008| 04:34 pm | Posted by hlee

Astronomers tend to think in Bayesian way, but their Bayesian implementation is very limited. OpenBUGS, WinBUGS, GeoBUGS (BUGS for geostatistics; for example, modeling spatial distribution), R2WinBUGS (R BUGS wrapper) or PyBUGS (Python BUGS wrapper) could boost their Bayesian eagerness. Oh, by the way, **BUGS** stands for **Bayesian inference Using Gibbs Sampling.** Continue reading ‘BUGS’ »

Tags:

openBUGS,

PyBUGS,

Python,

R,

toolbox,

winBUGS Category:

Algorithms,

Bayesian,

Data Processing,

Languages,

MCMC,

Methods,

News |

Comment
Aug 27th, 2008| 08:08 pm | Posted by hlee

PyIMSL is a collection of Python wrappers to the math and statistical algorithms in the IMSL C Numerical Library^{[1]}. I recall the days of digging in IMSL (International Mathematics and Statistics Library) user manuals and learning Fortran and C to use this vast library (Splus was to slow at that time). Upon knowing that Python is very favored among astronomers (click here to see the slog posts about Python) and that limits exist in Numerical Recipes (I didn’t check the latest version published last year, though), probably IMSL is useful for mathematical and statistical analysis for astronomers.

To know more, Continue reading ‘PyIMSL’ »

May 13th, 2008| 03:47 pm | Posted by hlee

The brackets could be filled with other languages but two are introduced today: **Perl** (perl.org) and **Python** (python.org). These two are widely used among astronomers and can be empowered by **R** (r-project.org). Continue reading ‘R-[{Perl,Python}] Interface’ »

Jan 22nd, 2007| 05:08 am | Posted by hlee

Both in astronomy and statistics, python is recognized as a versatile programming language. I asked python tutorials to Alanna. The following is her answer, which looks very useful for those who wish to learn python.

Continue reading ‘Learning Python’ »