Oct 15th, 2009| 06:46 pm | Posted by hlee

Astronomers rely on scatter plots to illustrate correlations and trends among many pairs of variables more than any scientists^{[1]}. Pages of scatter plots with regression lines are often found from which the slope of regression line and errors bars are indicators of degrees of correlation. Sometimes, too many of such scatter plots makes me think that, overall, resources for drawing nice scatter plots and papers where those plots are printed are wasted. Why not just compute correlation coefficients and its error and publicize the processed data for computing correlations, not the full data, so that others can verify the computation results for the sake of validation? A couple of scatter plots are fine but when I see dozens of them, I lost my focus. This is another cultural difference. Continue reading ‘Scatter plots and ANCOVA’ »

Tags:

ANCOVA,

ANOVA,

approximation,

correlation,

Gaussianity,

graphics,

MADS,

modeling,

nonparametric,

parallel coordinates,

PCA,

quality,

quantity,

regression,

scatter plots Category:

arXiv,

Cross-Cultural,

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Jargon,

Methods,

Stat,

Uncertainty |

Comment
Oct 13th, 2009| 03:15 pm | Posted by hlee

Although a bit of time has elapsed since my post space weather, saying that **logistic regression** is used for prediction, it looks like still true that **logistic regression** is rarely used in astronomy. Otherwise, it could have been used for the similar purpose not under the same statistical jargon but under the Bayesian modeling procedures. Continue reading ‘[MADS] logistic regression’ »

Oct 1st, 2009| 10:18 pm | Posted by hlee

I decide to discuss **Kalman Filter** a while ago for the slog after finding out that this popular methodology is rather underrepresented in astronomy. However, it is not completely missing from ADS. I see that the fulltext search and all bibliographic source search shows more results. Their use of **Kalman filter,** though, looked similar to the usage of “genetic algorithms” or “Bayes theorem.” Probably, the broad notion of **Kalman filter** makes it difficult my finding **Kalman Filter** applications by its name in astronomy since often wheels are reinvented (algorithms under different names have the same objective). Continue reading ‘[MADS] Kalman Filter’ »

Tags:

Cressie,

inference,

Kalman filter,

kriging,

MADS,

spatial statistics Category:

arXiv,

Astro,

Cross-Cultural,

Data Processing,

Imaging,

Jargon |

Comment
Sep 10th, 2009| 11:20 pm | Posted by hlee

Soon it’ll not be qualified for [MADS] because I saw some abstracts with the phrase, **compressed sensing** from arxiv.org. Nonetheless, there’s one publication within refereed articles from ADS, so far.

http://adsabs.harvard.edu/abs/2009MNRAS.395.1733W.

*Title:***Compressed sensing imaging techniques for radio interferometry**

*Authors:* Wiaux, Y. et al. Continue reading ‘[MADS] compressed sensing’ »

Tags:

compressed sensing,

ill-posed,

image reconstruction,

interferometry,

inverse problem,

MADS,

Nyquist-Shannon sampling theorem Category:

Algorithms,

Cross-Cultural,

Data Processing,

Imaging,

Jargon,

Spectral |

Comment
Sep 4th, 2009| 01:30 pm | Posted by hlee

ARCH (**autoregressive conditional heteroscedasticity**) is a statistical model that considers *the variance of the current error term to be a function of the variances of the previous time periods’ error terms*. I heard that this model made Prof. Engle a Nobel prize recipient. Continue reading ‘[MADS] ARCH’ »

Aug 25th, 2009| 09:19 pm | Posted by hlee

**Kriging** is the first thing that one learns from a spatial statistics course. If an astronomer sees its definition and application, almost every astronomer will say, “Oh, I know this! It is like the 2pt correlation function!!” At least this was my first impression when I first met **kriging.**

There are three distinctive subjects in spatial statistics: **geostatistics**, **lattice data analysis**, and **spatial point pattern analysis.** Because of the resemblance between the spatial distribution of observations in coordinates and the notion of spatially random points, spatial statistics in astronomy has leaned more toward the spatial point pattern analysis than the other subjects. In other fields from immunology to forestry to geology whose data are associated spatial coordinates of underlying geometric structures or whose data were sampled from lattices, observations depend on these spatial structures and scientists enjoy various applications from geostatistics and lattice data analysis. Particularly, **kriging** is the fundamental notion in **geostatistics** whose application is found many fields. Continue reading ‘[MADS] Kriging’ »

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BLUP,

book,

books,

CMB,

Cressie,

Diggle,

geostatistics,

hierarchical model,

kriging,

MADS,

point pattern analysis,

sparse,

spatial statistics,

Stein,

WMAP Category:

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Methods,

Stat |

Comment
Jun 4th, 2009| 04:36 pm | Posted by hlee

Please, do not confuse **adaptive filter** (hereafter, **AF**) with **adaptive optics** (hereafter, **AO**). I have no expertise in both fields but have small experiences to tell you the difference. Simply put, **AF** is comparable to software as opposed to **AO** to hardware, which is for constructing telescopes in order to collect data with sharpness and to minimize time varying atmospheric blurring. When you search **adaptive filter** in ADS you’ll more likely come across with **adaptive optics** and **notch filter**. Continue reading ‘[MADS] Adaptive filter’ »

Jun 1st, 2009| 09:51 pm | Posted by hlee

How would you assign orders to multivariate data? If you have your strategy to achieve this ordering task, I’d like to ask, “is your strategy **affine invariant**?” meaning that shift and rotation invariant. Continue reading ‘[MADS] data depth’ »

Tags:

break points,

data depth,

MADS,

mean,

median,

multivariate,

nonparametric,

order,

parasite,

quantile,

robust,

sort,

vertebrate Category:

Algorithms,

arXiv,

Cross-Cultural,

Jargon,

Stat |

Comment
May 28th, 2009| 11:54 pm | Posted by hlee

This simple law, despite my trial of full text search, was not showing in ADS. As discussed in systematic errors, astronomers, like physicists, show their error components in two additive terms; statistical error + systematic error. To explain such decomposition and to make error analysis statistically rigorous, the **law of total variance (LTV)** seems indispensable. Continue reading ‘[MADS] Law of Total Variance’ »

Tags:

additive,

bias,

law of total variance,

MADS,

mathematical statistics,

mean integrated square error,

mean square error,

MISE,

mse,

probability theory,

variance Category:

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Stat,

Uncertainty |

Comment
Apr 2nd, 2009| 12:00 pm | Posted by hlee

I cannot remember when I first met **Chernoff face** but it hooked me up instantly. I always hoped for confronting multivariate data from astronomy applicable to this charming EDA method. Then, somewhat such eager faded, without realizing what’s happening. Tragically, this was mainly due to my absent mind. Continue reading ‘[MADS] Chernoff face’ »

Tags:

calibration,

Capella,

Chandra,

Chernoff face,

EDA,

line ratios,

MADS,

XAtlas Category:

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2 Comments
Mar 9th, 2009| 05:18 pm | Posted by hlee

It bears the name of its inventor, Prasanta Chandra Mahalanobis. As opposed to the Euclidean distance, a household name, the name of this distance is rarely used but many pseudonyms exist with variations adapted into broad scientific disciplines and applications. Therefore, under different names, I believe that the Mahalanobis distance is frequently applied in exploring and analyzing astronomical data. Continue reading ‘[MADS] Mahalanobis distance’ »

Feb 9th, 2009| 03:16 pm | Posted by hlee

There were (only) four articles from ADS whose abstracts contain the word **semiparametric** (none in titles). Therefore, **semiparametric** is not exactly [MADS] but almost [MADS]. One would like to say it is virtually [MADS] or quasi [MADS]. By introducing the term and providing rare examples in astronomy, I hope this scarce term **semiparametric** to be used adequately against its misguidance of astronomers to inappropriate usage for statistical inference with their data. Continue reading ‘[MADS] Semiparametric’ »

Dec 11th, 2008| 03:46 pm | Posted by hlee

A few scientists in our group work on estimating the intensities of gamma ray observations from sky surveys. This work distinguishes from typical image processing which mostly concerns the point estimation of intensity at each pixel location and the size of overall white noise type error. Often times you will notice from image processing that the orthogonality between errors and sources, and the white noise assumptions. These assumptions are typical features in image processing utilities and modules. On the other hand, CHASC scientists relate more general and broad statistical inference problems in estimating the intensity map, like intensity uncertainties at each point and the scientifically informative display of the intensity map with uncertainty according to the Poisson count model and constraints from physics and the instrument, where the field, **multiscale modeling** is associated. Continue reading ‘[MADS] multiscale modeling’ »

Dec 7th, 2008| 11:23 pm | Posted by hlee

MADS stands for **“Missing in ADS.”** Every astronomer, I believe, knows what ADS is. As we have [EotW] series and used to have [ArXiv] series, creating a new series for semi-periodic postings under the well known name ADS seems interesting. Continue reading ‘[MADS] HMM’ »