## mvabund – new R pkg for multivariate abundance data

March 19, 2012
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There is a new R package in town, mvabund, which does, as they say "statistical methods for analysing multivariate abundance data". The authors introduced the paper in an online early paper in Methods in Ecology and Evolution here, R package here. Th...

## Backtesting Asset Allocation portfolios

March 18, 2012
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$Backtesting Asset Allocation portfolios$

In the last post, Portfolio Optimization: Specify constraints with GNU MathProg language, Paolo and MC raised a question: “How would you construct an equal risk contribution portfolio?” Unfortunately, this problem cannot be expressed as a Linear or Quadratic Programming problem. The outline for this post: I will show how Equal Risk Contribution portfolio can be

## Independent measures (between-subjects) ANOVA and displaying confidence intervals for differences in means

March 18, 2012
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$Independent measures (between-subjects) ANOVA and displaying confidence intervals for differences in means$

In Chapter 2 (Confidence Intervals) of Serious stats I consider the problem of displaying confidence intervals (CIs) of a set of means (which I illustrate with the simple case of two independent means). Later, in Chapter 16 (Repeated Measures ANOVA), I consider the trickier problem of displaying of two or more means from paired or

## A graphical overview of your MySQL database

March 18, 2012
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If you use MySQL, there’s a default schema called ‘information_schema‘ which contains lots of information about your schemas and tables among other things. Recently I wanted to know whether a table I use for storing the results of a large … Continue reading →

## Liking of apples – more than juiciness

March 18, 2012
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In a previous blog it was shown using literature data that liking of apples was related to juiciness. However, there were some questionsIs the relation linear or slightly curved? The variation in liking around CJuiciness is large. Are more explana...

## Useful R snippets

March 18, 2012
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In this post we collect several R one- or few-liners that we consider useful. As our minds tend to forget these little fragments we jot them down here so we will find them again. Indexing in nested loops Every once in a while I run a nested loop like the following one. Now if I

## How to read an excel file (dot xls and dot xlsx) into a data frame with r

March 17, 2012
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how to read an excel file (dot xls and dot xlsx) into a data frame with r

## Predicting Marketing Campaign with R

March 17, 2012
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In my last blog I created a mechanism to fetch data from Salesforce using rJava and SOQL. In this blog I am going to use that mechanism to fetch ad campaign data from salesforce and predict future ad campaign sales using R Let us assume that Salesforce has campaign data for last eight quarters.  This

## Logistic map: Feigenbaum diagram

March 17, 2012
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The other day I found some old basic code I had written about 15 years ago on a Mac Classic II to plot the Feigenbaum diagram for the logistic map. I remember, it took the little computer the whole night to produce the chart.With today's computers even...

## Solving easy problems the hard way

March 17, 2012
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There’s a charming little brain teaser that’s going around the Interwebs. It’s got various forms, but they all look something like this: This problem can be solved by pre-school children in 5-10 minutes, by programer – in 1 hour, by people with higher education … well, check it yourself!  8809=6 7111=0 2172=0 6666=4 1111=0 3213=0 7662=2 9313=1 0000=4 2222=0 3333=0 5555=0 8193=3 8096=5 7777=0 9999=4 7756=1 6855=3 9881=5 5531=0 2581=? SPOILER ALERT… The answer has to do with how many

## Savitzky-Golay filters in R

March 17, 2012
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Derivatives are a good way to extract information to our spectra. As we know NIR contents overlapping bands, and spectra must be treated with math operations in order to extract as much information as possible and to correlate it with the constituent &...

## Cooling Stations

March 17, 2012
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Over the course of the past few years I have taking a look at cooling stations a few times but never in much depth. A few other people have looked at them, but usually without much rigor. The standard approach is to find some cooling stations and then conclude that somehow global warming is thereby

## Dates and times in R

March 16, 2012
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Nothing looks funnier than a patchy simian. That's why we sighed a great sigh of relief when we spotted this article on the lubridate package in R. It saves a great deal of hair pulling.http://www.r-statistics.com/2012/03/do-more-with-dates-and-times...

## simulated annealing for Sudokus [2]

March 16, 2012
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On Tuesday, Eric Chi and Kenneth Lange arXived a paper on a comparison of numerical techniques for solving sudokus. (The very Kenneth Lange who wrote this fantastic book on numerical analysis.) One of these techniques is the simulated annealing approach I had played with a long while ago.  They seem to use the same penalisation

## Simplify working with times and dates in R

March 16, 2012
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R has some very powerful built-in features for working with dates, times, and time-zones. But power and flexibility rarely correlate with ease-of-use, and this is no exception. The lubridate package comes to the rescue, make things a bit easier when working with chronological data in R. The paper Dates and Times Made Easy with lubridate provides in-depth explanations of...

## Montreal R Workshop: Likelihood Methods and Model Selection

March 16, 2012
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Monday, March 19, 2012  14h-16h, Stewart Biology N4/17 Corey Chivers, McGill University Department of Biology This workshop will introduce participants to the likelihood principal and its utility in statistical inference.  By learning how to formalize models through their likelihood function, participants will learn how to confront these models with data in order to make statistical

March 16, 2012
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Here is another data downloading and parsing script, this one for the Dow Jones/UBS Commodities Indexes. Compared to the last post, this parser deals with multiple sheets and multiple columns in each sheet. It also constructs monthly series from the daily data, and stores it using a different symbol. Finally, it’s a good example of

## Do more with dates and times in R with lubridate 1.1.0

March 16, 2012
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This is a guest post by Garrett Grolemund (mentored by Hadley Wickham) Lubridate is an R package that makes it easier to work with dates and times. The newest release of lubridate (v 1.1.0) comes with even more tools and …Read more »

## digest 0.5.2

March 15, 2012
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A new version of the digest package (which generates hash function summaries for arbitrary (and possibly nested) R objects using any of the standard md5, sha-1, sha-256 or crc32 algorithms) is now on CRAN. Murray Stokely noticed a corner case where...

## A No BS Guide to the Basics of Parallelization in R

March 15, 2012
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What is parallelization?Parallelization is using multiple processing cores to, hopefully, make your programs run faster than serial code, which is the use of just one processing core. Parallel code is not always faster than its serial counterpart (but if you're doing it right and you're careful about what you parallelize, it will be --- remember, that's your goal here). ...

## p curves revisited

March 15, 2012
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I finally found some time to take a closer look at p curves. I haven't had a chance to follow-up my simulations (and probably won't for a few weeks if not months), but I have had time to think through the ideas the p curve approach raises based on some of the comments I've received and a brief exchange...

## R gotcha for the week

March 15, 2012
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I use the biomaRt package from Bioconductor in almost every R session. So I thought I’d load the library and set up a mart instance in my ~/.Rprofile: On starting R, I was somewhat perplexed to see this error message: Twitter to the rescue. @hadleywickham told me to load utils first and @vsbuffalo explained that

## Europe most dangerous cities

March 15, 2012
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When I was searching for data about U.S prison population, for another post, I run across eurostat, a nice source for data to play around with. I pooled some numbers, specifically homicides recorded by the police. A panel data for … Continue reading →

## SAP integrates R with HANA

March 15, 2012
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We can add SAP to the list of vendors offering R integration with their products. InformationWeek reports that the new SAP BusinessObjects Predictive Analysis model provides a graphical user interface to R. Created in reaction to "competitive and market forces, including the momentum of open source R", the new module provides in-database processing (presumably by embedding R within HANA...

## Liking of apples – some data to link

March 15, 2012
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I browsed through a paper by Peneau et al. (J. Sensory Studies, 2007) where they have nice data on apples; consumer evaluation, sensory evaluation and instrumental measurements. I think these are interesting data to examine if these variable blocks can...

## The Anachronism Machine: The Language of Downton Abbey

March 15, 2012
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I've recently become hooked on the TV series Downton Abbey. I'm not usually one for costume dramas, but the mix of fine acting, the intriguing social relationships, and the larger WW1-era story make for compelling viewing. (Also: Maggie Smith is a treasure.) Despite the widespread criticial acclaim, Downton has met with criticism for some period-innapropriate uses of language. For...

## Opinions Not Backed by Money Updated Again

March 15, 2012
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Strange that I am updating this post for a third time and nothing really has changed, but the fact that nothing has changed is incredibly interesting to me.  Since it is an update, I will not duplicate the explanation, so please read the last vers...

## A Graphical Explanation of how to Interpret a Dendrogram

March 15, 2012
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Dendrograms are a convenient way of depicting pair-wise dissimilarity between objects, commonly associated with the topic of cluster analysis. This is a complex subject that is best left to experts and textbooks, so I won't even attempt to cover it her...