266 search results for "PCA"

Estimating Missing Data with aregImpute() {R}

April 19, 2010
By

  Missing Data Soil scientists routinely sample, characterize, and summarize patterns in soil properties in space, with depth, and through time. Invariably, some samples will be lost or sufficient funds required for complete characterization can run out. In these cases the scientist is left with a data table that contains holes (so to speak) in the rows/columns that are...

Read more »

alphahull: an R Package for Alpha-Convex Hull

April 16, 2010
By
alphahull: an R Package for Alpha-Convex Hull

new paper on the α-convex hull appeared in the Journal of Statistical Software today (http://www.jstatsoft.org/v34/i05/paper). The α-convex hull is an interesting problem which caught my attention long time ago but I didn’t know a solution then. R has a function chull() which can generate (indices of) the convex hull for a series of points. Now

Read more »

REvolution R Community 3.2 now available

April 9, 2010
By

REvolution R Community, REvolution's free distribution based on R from the R Project, has been updated to version 3.2 and is now available for download for Windows and MacOS. Some features of this release include: Upgraded R engine. This release is based on R 2.10.1, the latest release (as of this writing). This brings many new features to the...

Read more »

Demonstrating the Power of F Test with gWidgets

April 2, 2010
By

e know the real distribution of the F statistic in linear models — it is a non-central F distribution. Under H0, we have a central F distribution. Given 1 – α, we can compute the probability of (correctly) rejecting H0. I created a simple demo to illustrate how the power changes as other parameters vary,

Read more »

Looking for Software Paths in Windows Registry

March 28, 2010
By
Looking for Software Paths in Windows Registry

hen we want to call external programs in R under Windows, we often need to know the paths of these programs. For instance, we may want to know where ImageMagick is installed, as we need the convert (convert.exe) utility to convert images to other formats, or where OpenBUGS is installed because we need this path

Read more »

A Demo for the Ratio Estimation in Sampling Survey (Animation)

March 24, 2010
By
A Demo for the Ratio Estimation in Sampling Survey (Animation)

mber Watkins gave me a suggestion on the animation for the ratio estimation, and I think this is a good topic for my animation package. I’ve finished writing the initial version of the function sample.ratio() for this package, which will appear in the version 1.1-2 a couple of days later. As we know, the benefit

Read more »

Font Families for the R PDF Device

March 24, 2010
By

otivated by the excellent R package pgfSweave, I begin to notice the font families in my graphs when writing Sweave documents. The default font family for PDF graphs is Helvetica, which is, in most cases (I think), inconsistent with the LaTeX font styles. Some common font families are listed in ?postscript, and we can take

Read more »

Guess the Random Seed

March 12, 2010
By

tephanie asked in 511 today if we were able to get the random seed which was set by set.seed() but we were only given the random numbers (without knowing the seed). This kind of “hacker” questions sound interesting. One dirty solution should be the brute-force method, e.g: # x: the random vector; # FUN: the

Read more »

A quicky..

February 22, 2010
By

If you’re (and you should) interested in principal components then take a good look at this. The linked post will take you by hand to do everything from scratch. If you’re not in the mood then the dollowing R functions will help you. An example. # Generates sample matrix of five discrete clusters that have

Read more »

Press Enter in LyX Sweave as You Wish

February 18, 2010
By
Press Enter in LyX Sweave as You Wish

or a long time I’ve been wondering why we are not able to use Enter in the LyX Scrap environment which was set up by Gregor Gorjanc for Sweave. Two weeks ago, I (finally!) could not help asking Gregor about this issue, as I’m using “LyX + Sweave” more and more in my daily work.

Read more »