# VOStat: FAQ

## What analyses can VOStat do?

Transforming and subsetting the data
• Select cases
• Simple transform
Plots and summaries
• Boxplot: A univariate plot giving a rough idea of the distributions and outliers.
• Dotplot: Plotting values of the same variable for different objects (e.g., densities of different asteroids).
• Histogram: Univariate histogram.
• Averaged Shifted Histogram (ASH): Univariate ASH.
• Scatterplot: A bivariate plot allowing error bars.
• Make a pairs plot. This is sometimes also called a ScatterPLOt Matrix or SPLOM.
• 3D scatterplot
• Summary statistics
Estimating distribution from data
• Histogram
• Averaged Shifted Histogram (ASH): Univariate ASH.
• Empirical distributon function (ECDF)
• Kernel density estimation:
• 1-dimensional (fixed window width)
• 2-dimensional
• Fiting parametric distribution
Comparing data with distributions
• Normal plot
• Tests for normality
• 1-sample KS test. This is useful for checking if a variable in your data set is distributed according to some standard distribution.
• Anderson-Darling test. This is another test for checking if a variable in your data set is distributed according to some standard distribution.
• 2-sample KS test to compare the distributions of two continuous variables in a data set.
• Chi-square 2 sample test to compare the distributions of two discrete variables in a data set.
Some standard tests
• One sample z-test to compare the mean of a variable with some given number. This test is applicable only if you know (or have a very good approximation for) the standard deviation of your variable. (Requires Gaussianity assumption.)
• One sample t-test. Similar to above, except that you do not need to know the standard deviation. (Requires Gaussianity assumption.)
• paired t-test for comparing the means of two variables. (Requires Gaussianity assumption.)
• Wilcoxon's signed rank test (1 sample). Much like one sample t-test, but without the Gaussianity assumption.
• Wilcoxon's signed rank test (2 sample). Much like paired t-test, but without the Gaussianity assumption.
Regression
• Linear regression
• Major axis/orthogonal regression
• LOESS
• Linear quantile regression
• Robust regression using M estimation
• Robust regression using trimmed least squares
• Theil-Sen regression
Multivariate methods
• Make a pairs plot. This is sometimes also called a ScatterPLOt Matrix or SPLOM.
• Linear regression
• Principal component analysis
• Canonical correlation analysis
• Model based clustering
• Hierarchical clustering
Spatial methods
• Variogram
• k-nearest neighbours and Moran's I testa
• Ripley's K and related measures
• Voronoi tesselation and adaptive 2D kernel density estimation
Directional statistics
• Plotting directional data
• Summarizing direction data
• Kernel density estimation
• Fitting a von Mises distribution
• Testing goodness-of-fit with a von Mises distribution
• Testing goodness-of-fit with uniform distribution
Survival analysis
• Maximum likelihood Kaplan-Meier estimate of the survival curve for censored data
• A bunch of tests for censored data: Log rank, Peto-Peto, Kolmogorov-Smirnov, Cramer-von Mises, and Anderson-Darling tests
• Maximum likelihood Lynden-Bell-Woodroofe estimator
Time series analysis
• Time series plotting with smoothing
• (Partial) AutoCorrelation Function (ACF and PACF)
• Autoregressive modelling
• Periodogram with smoothing option

## What data file formats are supported by VOStat?

VOStat is for analysis of catalog data (and not image/spectrum data). VOStat reads ASCII (space/tab/comma separated) files, FITS files, and VOTables.

VOStat uses different output formats for different purposes:

• graphical output: png, eps and pdf.
• R scripts: ASCII text, that you can copy-n-paste from the webpage.
• R workspace: Binary R format.

## How does VOStat handle mising values?

Please see our missing data policy for details.

## What is SAMP?

SAMP stands form Simple Application Management Protocol. It is a server-client protocol designed to coordinate between various applications running in the same machine. You may get the details here.

## Which SAMP MTypes does VOStat support?

```samp.app.ping
samp.hub.disconnnect