Negative Scalability Coefficients in Excel

May 12, 2009
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Negative Scalability Coefficients in Excel

Recently, several performance engineers, who have been applying my universal scalability law (USL) to their throughput measurements, reported a problem whereby their Excel spreadsheet calculations produced a negative value for the coherency parameter (...

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Packages featured with Inference for R

May 12, 2009
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Packages featured with Inference for R

quantmod, TTR, and xts were (not so) recently featured on the Inference for R Blog. Inference for R is a Integrated Development Environment (IDE) designed specifically for R.The post gives an example of how to easily perform advanced financial stock a...

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Analytic Infrastructure – Three Trends

May 11, 2009
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This is a post about systems, applications, services and architectures for building and deploying analytics. Sometimes this is called analytic infrastructure. In this post, we look at several trends impacting analytic infrastructure. Trend 1. Open source analytics has reached Main Street. R, which was first released in 1996, is now

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Analytic Infrastructure – Three Trends

May 11, 2009
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Analytic Infrastructure – Three Trends

This is a post about systems, applications, services and architectures for building and deploying analytics. Sometimes this is called analytic infrastructure. In this post, we look at several trends impacting analytic infrastructure. Trend 1. Open source analytics has reached Main Street. R, which was first released in 1996, is now

Read more »

Analytic Infrastructure – Three Trends

May 11, 2009
By
Analytic Infrastructure – Three Trends

This is a post about systems, applications, services and architectures for building and deploying analytics. Sometimes this is called analytic infrastructure. In this post, we look at several trends impacting analytic infrastructure. Trend 1. Open source analytics has reached Main Street. R, which was first released in 1996, is now

Read more »

vim plugin for R

May 11, 2009
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vim plugin for R

For the vim/R-addicted a must to have: http://www.vim.org/scripts/script.php?script_id=2628

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Searching through mailing list archives

May 8, 2009
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Searching through mailing list archives

Romain Francois on his blog posted a very useful function to search through the R mailing list archives. Take a look at it here. Take also a look at the tm package introduced in  R News, 8(2):19–22, Oct. 2008 with an example dealing with analysi...

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Region Of Interest analysis of BOLD data

Region Of Interest analysis of BOLD data

For my research I do Region-Of-Interest (ROI) analyses of BOLD fMRI data. That is, we look at how brain activity develops in certain predefined brain regions during an experiment. On this site I describe a script that automates these analyses, using SP...

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Resources for Learning R in Iraq?

May 6, 2009
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Resources for Learning R in Iraq?

Please comment on this if you know of Arabic and Kurdish language resources for learning R. I have been encouraging the economics faculty here to learn R for econometrics, both on grounds of quality and cost. Here is a short list of resources that can help new users make the transition from SPSS if they

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SNA with R: Loading large networks using the igraph library

May 6, 2009
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SNA with R: Loading large networks using the igraph library

We are interested in Social Network Analysis using the statistical analysis and computing platform R. The documentation for R is voluminous but typically not very good, so this entry is part of a series where we document what we learn as we explore the tool and the packages. In our previous post on SNA we gave up...

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R Reference Card (PDF)

May 5, 2009
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Last week I posted a short tutorial on how to merge datasets using R. R is a free and open-source statistical computing software and programming language (get R here). The only downside is a steeper learning curve because the documentation is sparse and often difficult to understand at first. Once you start using it, you'll realize...

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05.05.09: 6 Steps to call a C function in R

May 5, 2009
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TasksWrap for netMotifsSubmit Abstract for PhD RetreatRead Architecture paperÖzgür's WST data and Uli's RTCA dataAfter some searching and testing, I have began to know how to call a C function in R. The reason for doing this can be speed (for example, the convolution of two finite sequences, as raised by the Writing R Extensions tutorial, refered as...

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R/Finance 2009 Presentations Online

May 4, 2009
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R/Finance 2009 Presentations Online

Posted to the R-SIG-Finance mailing list today:For those who missed it, the slides for the R/Finance 2009 tutorialsand presentations are now available on RinFinance.comhttp://www.RinFinance.com/presentationsWe want to thank everyone who traveled to Chi...

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Colouring a 3D plot according to z-values

May 3, 2009
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Colouring a 3D plot according to z-values

Here is a script that colors a 3D plot according to the z value (height) of each point. persp.withcol <- function(x,y,z,pal,nb.col,...,xlg=TRUE,ylg=TRUE) { colnames(z) <- y rownames(z) <- x nrz <- nrow(z) ncz <- ncol(z) color <- pal(nb.col) zfacet <- z + z + z + z facetcol <- cut(zfacet, nb.col) par(xlog=xlg,ylog=ylg)

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An algorithm to find local extrema in a vector

May 3, 2009
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An algorithm to find local extrema in a vector

I spend some time looking for an algorithm to find local extrema in a vector (time series). The solution I used is to “walk” through the vector by step larger than 1, in order to retain only one value even when the values are very noisy (see the picture at the end of the post).

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Brad Mehldau at the CSO

Just got home from a wonderful concert by Brad Mehldau at the CSO. This was long overdue as I kept reading about Mehldau. And even though he performs quite regularly around here, I had never seen him. Big mistake. The first set was performed as a (strictly acoustic) trio with Larry Grenadier on bass and Jeff Ballard on drums. After several compositions...

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RSI(2) with Position Sizing

May 1, 2009
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RSI(2) with Position Sizing

Though it's more than two weeks later, here's the second post in the series that will demonstrate how to build, test, and implement a trading strategy with R. You can find the first post here.The first post replicated this simple RSI(2) strategy from ...

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GSoC 2009 Chicago area meeting

April 30, 2009
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Thanks to the effort of the tireless Borja Sotomayor for the local ACM chpater as well as the good folks at Google in Chicago, we had a local kickoff meeting for this year's Google Summer of Code at Google's Chicago office. A few accepted GSoC students...

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GSoC 2009 Chicago area meeting

April 30, 2009
By

Thanks to the effort of the tireless Borja Sotomayor for the local ACM chpater as well as the good folks at Google in Chicago, we had a local kickoff meeting for this year's Google Summer of Code at Google's Chicago office. A few accepted GSoC students, mentors, and a few Google engineers gave short presentations to a bunch of ACM-affiliated students from U of...

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Slides from most recent R and HPC tutorial

April 29, 2009
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A little earlier I put the slides from my Introduction to High-Performance Computing with R tutorial at the R / Finance conference last week onto my talks / presentation page. Other tutorials, talks and keynotes are also being posted on the conference...

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Slides from most recent R and HPC tutorial

April 29, 2009
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A little earlier I put the slides from my Introduction to High-Performance Computing with R tutorial at the R / Finance conference last week onto my talks / presentation page. Other tutorials, talks and keynotes are also being posted on the conference program page. This tutorial was a shorter format of just an hour which did not allow for any parallel...

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Babylonian confusion or flexibility?

April 29, 2009
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Babylonian confusion or flexibility?

As we are used from UNIX. there is not one single suitable solution to solve a problem, but usually a few different ways to do “the same”. Depending on what commands we know (best), we will chose the one or the other solution. Only the absolute expert will be able to choose the most efficient

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Rails, Scalability and Sexism

April 29, 2009
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It’s been a long time since I posted here, for a number of reasons: Change of focus from Ruby programming to Linux capacity planning, especially in the realm of I/O subsystems. You’ll find more about that at http://linuxcapacityplanning.com...

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screen in ubuntu 9.04

April 29, 2009
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screen in ubuntu 9.04

As I told in a previous post, I consider the unix tool screen essential for my work. It seems that the just released Ubuntu 9.04  contains a package that make it easier to configure and use. You can find the full story here.

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Introducing Influence.ME: Tools for detecting influential data in mixed models

April 29, 2009
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I’m highly excited to announce that influence.ME is now available. Influence.ME is a new software package for R, providing statistical tools for detecting influential data in mixed models. It has been developed by Rense Nieuwenhuis, Ben Pelzer, a...

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Google Summer of Code 2009: R / Quantlib

April 28, 2009
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With everything that has been going on of late, I have yet to mention that Khanh Nguyen, a Ph.D. student in Computer Science at U Mass / Boston, will be working with me on RQuantLib as part of the Google Summer of Code program this year. We had twenty...

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Google Summer of Code 2009: R / Quantlib

April 28, 2009
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With everything that has been going on of late, I have yet to mention that Khanh Nguyen, a Ph.D. student in Computer Science at U Mass / Boston, will be working with me on RQuantLib as part of the Google Summer of Code program this year. We had twenty-two applications to review for the R project, including three for the RQuantLib...

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2009 Chambers award winner announced

April 28, 2009
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We are pleased to announce that the judges of the Chambers Award have selected the winner of the 2009 competition: Yihui Xie, from the Renmin University of China. Yihui received this year's award for his submission "animation," an R package for using g...

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2009 Chambers award winner announced

April 28, 2009
By

We are pleased to announce that the judges of the Chambers Award have selected the winner of the 2009 competition: Yihui Xie, from the Renmin University of China. Yihui received this year's award for his submission "animation," an R package for using g...

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