Review: Kölner R Meeting 18 October 2013

The Cologne R user group met last Friday for two talks on split apply combine in R and XLConnect by Bernd Weiß and Günter Faes respectively, before the usual Schnitzel and Kölsch at the Lux.

Split apply combine in R

The apply family of functions in R is incredible powerful, yet for newcomers often somewhat mysterious. Thus, Bernd gave an overview of the different apply functions and their cousins. The various functions differ in their object inputs, e.g. vectors, arrays, data frames or lists, and their outputs. Other related functions are by, aggregate and ave. While functions like aggregate reduce the output size, others like ave will return as many rows as the input object and repeat the results where necessary.

Alternatively to the base R function Bernd touched also on the **ply functions of the plyr package. The function names are certainly easier to remember, but their syntax can be a little awkward (.()). Bernd's slides, in German, are already available from our Meetup site.

XLConnect

When dealing with data stored in spreadsheets most member of the group rely on read.csv and write.csv in R. However, if you have a spreadsheet with multiple tabs and formatted numbers, read.csv becomes clumsy, as you would have to save each tab without any formatting in separate files.

Günter presented the XLConnect as an alternative to read.csv or indeed RODBC for reading spreadsheet data. It uses the Apache POI API as the underlying interface. XLConnect requires a Java runtime environment on your computer, but no installation of Excel. That makes it a true platform independent solution to exchange data with spreadsheets and R. Not only can you read defined rows and columns from Excel into R, or indeed named ranges, but in the same way data can be stored in Excel files again and to top it all - also graphic output from R.

Next Kölner R meeting

The next meeting is scheduled for 13 December 2013. A discussion of the data.table package is already on the agenda.

Please get in touch if you would like to present and share your experience, or indeed if you have a request for a topic you would like to hear more about. For more details see also our Meetup page.

Thanks again to Bernd Weiß for hosting the event and Revolution Analytics for their sponsorship.

Next Kölner R User Meeting: 18 Oktober 2013

Quick reminder: The next Cologne R user group meeting is scheduled for this Friday, 18 October 2013. We will discuss and hear about the apply family of functions and the XLConnect package. Further details and the agenda are available on our KölnRUG Meetup site. Please sign up if you would like to come along. Notes from past meetings are available here.

Thanks to Revolution Analytics, who sponsors the Cologne R user group as part of their vector programme.

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Review: Kölner R Meeting 19 July 2013

Despite the hot weather and the beginning of the school holiday season in North Rhine Westphalia the Cologne R user group met yet again for two fascinating talks and beer and schnitzel afterwards.

Analysing Twitter data to evaluate the US Dollar / Euro exchange rates

Dietmar Janetzko presented ideas to forecast US Dollar / Euro exchange rate movements for the following day.

To forecast exchange rate movements, Dietmar distinguishes two school of thoughts. The first one is based on the analysis of fundamental analysis, e.g. figures of GDP, debt, unemployment, etc. and the other one is based on news, e.g. announcements from central banks, e.g. from Ben Bernanke and other industry experts.

While the data for the fundamental analysis is usually updated slowly, e.g. annually or quarterly, news can be of higher frequency and less regular. As a result the forecasting horizon in a very liquid market, as the forex market, can vary from one minute or less to next year or decade.

Dietmar's aim was to forecast the exchange rate for the following day and to outperform the forecast of a random walk. For his experiment he used daily exchange rates from Quandl, which has a nice R interface, and Twitter data from topsy, which gives him access to Twitter's 'firehose'.

For his analysis Dietmar focused on the number of tweets of the terms Euro + Crisis + <concept>, whereby he used a dictionary of nearly 600 different concept words.

His training algorithms used functions of the following packages: forecast, caret and car, looking for predictors that have a smaller error than a random error.

It goes without saying that Dietmar hasn't made millions from his algorithms yet, but the discussion and the end of his presentation will hopefully have given him a few pointers to do just that.

Graphs in R

Afshin Sadeghi, who has a background in Steiner tree methods for Protein-Protein interaction networks, gave an overview of the various graph packages in R. He started his talk with a little overview of the graph terminology of nodes, edges, trees, directed and undirected graphs.

Afshin then gave a brief overview of the various graph packages in R and the different visualisation options. The most popular package seems to be igraph, maintained by Gabor Csardi. Although different packages use sometimes different graph objects, there are often conversation tools available, e.g. igraph.to.graphNEL, allowing users to use the best algorithms from all packages.

You can access Afshin's slides via our Meetup site.

Next Kölner R meeting

The next meeting has been scheduled for 18 October 2013.

Please get in touch if you would like to present and share your experience, or indeed if you have a request for a topic you would like to hear more about. For more details see also our Meetup page.

Thanks again to Bernd Weiß for hosting the event and Revolution Analytics for their sponsorship.

Review: Kölner R Meeting 12 April 2013

Our 5th Cologne R user group meeting was the best attended meeting so far, with 20 members finding their way to the Institute of Sociology for two talks by Diego de Castillo on shiny and Stephan Holtmeier on cluster analysis, followed by beer and schnitzel at the Lux, a gastropub nearby.

Shiny

Diego gave an overview of the design principles behind shiny, which provides a powerful API to build web apps in pure R. His explanation of the reactive programming model was particularly helpful to understand how shiny works under the hood and why it is so responsive. His live demonstrations of shiny even included shiny server, which he had running in a virtual machine. Diego's slides are available via our Meetup site.

Diego de Castillo: Introduction to shiny

You can hear more from Diego and me at the UseR!2013 conference in Albacete, where we will give a googleVis tutorial. We will touch on googleVis on shiny as well. A dedicated shiny tutorial will be given in the afternoon by Josh and Winston from RStudio.

Cluster analysis

Stephan Holtmeier, who is a psychologist by background, presented an introduction to cluster analysis with R, motivated by his work in analysing survey data. As a toy example he used a 360° feedback survey of a group of managers within a big company. In his example he wanted to understand the profile of those managers better. Stephan illustrated how a cluster analysis can help to identify groups of managers with similar strengths, e.g. for communication, leadership and/or performance. Depending on how he measured the distance between managers he could look for people who have similar levels of competency or a similar profile (correlation). Stephan also touched on the differences between hierarchical and centroid based cluster analysis, such as k-means. You can find Stephan's slides (in German) also on our Meetup site.

Stephan Holtmeier: Cluster Analysis with R

For more information on cluster analysis functions in R see also the cluster task view on CRAN. If you would like to get an overview of how psychologists look at data, then check out William Revelle's vignette of the psych package. Finally, if you are interested in how a k-means cluster analysis can be used for image manipulation, see an earlier post of mine.

Next Kölner R meeting, 19 July 2013

The next meeting has been scheduled for 19 July. Günter Faes will present his experiences using the XLConnect package as an interface between R and Excel. Dietmar Janetzko agreed to present how he used R and Twitter to predict exchange rate movements. Of course, the evening will close with a few Kölsch in a nearby beer-garden.

Please get in touch if you would like to present and share your experience, or indeed if you have a request for a topic you would like to hear more about. For more details see also our Meetup page.

Thanks again to Bernd Weiß for hosting the event and Revolution Analytics for their sponsorship.

Next Kölner R User Meeting: 12 April 2013

Quick reminder: The next Cologne R user group meeting is scheduled for this Friday, 12 April 2013. We will discuss cluster analysis and shiny. Further details and the agenda are available on our KölnRUG Meetup site. Please sign up if you would like to come along. Notes from the last Cologne R user group meeting are available here.

Thanks also to Revolution Analytics, who sponsors the Cologne R user group as part of their vector programme.

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Review: Kölner R Meeting 6 February 2013

The fourth Cologne R user meeting took place last Wednesday at the Institute of Sociology. Thanks to Bernd Weiß for hosting the event and Revolution Analytics for their sponsorship.

We had two fantastic talks by Klaus Jacobi and M.eik Michalke. Klaus talked about Eliminating cloud pixels in satellite images via chronological interpolation and Meik presented his new roxyPackage package, which makes it even easier to maintain R packages with roxygen2.

Eliminating cloud pixels in satellite images via chronological interpolation

Klaus gave a great case study about his consulting work as a water engineer in Asia, where he used R to analyse the snow melting process in the mountains of Pakistan.

Images of snow melting over time. Klaus Jacobi

About half of the fresh water in some regions of Pakistan is sourced from snow meting during the spring season. The water is captured in dams and as the snow only melts slowly the water supply is much more predictable than the water from the monsoon season, which is the other key source of fresh water during the year.
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Next Kölner R User Meeting: 6 February 2013

Quick reminder: The next Cologne R user group meeting is scheduled for tomorrow, 6 February 2013. All details and the agenda are available on the KölnRUG Meetup site. Please sign up if you would like to come along. Notes from the last Cologne R user group meeting are available here.

Thanks also to Revolution Analytics, who are sponsoring the Cologne R user group as part of their vector programme.

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Review: Kölner R Meeting 5 October 2012

The third Cologne R user meeting took place last Friday, 5 October 2012, at the Institute of Sociology.

The evening was sponsored by Revolution Analytics, who provided funding which went towards the Kölner R user group Meetup page. We had a good turn-out with 18 participants showing up and three talks by Dominik Liebl, Jonas Stein and Sarah Westrop.

Photos: Günter Faes

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Next Kölner R User Meeting: 5 October 2012

The next Cologne R user group meeting is scheduled for 5 October 2012. All details and the agenda are available on the KölnRUG Meetup site. Please sign up if you would like to come along. Notes from the last Cologne R user group meeting are available here.

Thanks also to Revolution Analytics, who are sponsoring the Cologne R user group as part of their vector programme.

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Review: Kölner R Meeting 6 July 2012

The second Cologne R user meeting took place last Friday, 6 July 2012, at the Institute of Sociology. Thanks to Bernd Weiß, who provided the meeting room, we didn't have to worry about the infrastructure, like we did at our first gathering.

Again, we had an interesting mix of people turning up, with a very diverse background from chemistry to geo-science, energy, finance, sociology, pharma, physics, psychology, mathematics, statistics, computer science, telco, etc. Yet, the gender mix was still somewhat biased, with only one female attendee.

We had two fantastic talks by Bernd Weiß and Stephan Sprenger. Bernd talked about Emacs' Org-Mode and R. He highlighted the differences between literate programming and reproducible research and if you follow his slides, you get the impression that Emacs with Org-mode is the all-singing-all-dancing editor, or for those who speak German: eine eierlegende Wollmilchsau.

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Next Kölner R User Meeting: 6 July 2012

The next Cologne R user group meeting is scheduled for 6 July 2012. All details are available on the new KölnRUG Meetup site. Please sign up if you would like to come along, and notice that there is also pub poll for the after "work" drinks. Notes from the first Cologne R user group meeting are available here.

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Review: Kölner R Meeting 30 March 2012

The first Kölner R user meeting was great fun. About 20 useRs had turned up to exchange their ideas, questions and experience with R. Three talks about R & Excel, ggplot2 & XeLaTeX and Dynamical systems with R & simecol had kicked off the evening, with Kölsch (beer) losing our tongues further.

Thankfully a lot of people had brought along their laptops, as unfortunately we lacked a cable to connect any of the computers to the installed projector. Never-mind, we cuddled up around the notebooks and switched slides on the speakers sign.

Photos: Günter Faes

Similar to LondonR, it was a very informal event. Maybe slightly forced by myself, as I called everyone by his/her first name, which could be considered rude in Germany. But what I had noticed in London, and the same was true also in Cologne, was that people with a very diverse background and of all ages would meet to discuss matters around R, often not working in the same field. So why worry about hierarchies?

Most attendees were not R experts, but users in its pure sense, trying to solve real life problems, and I suppose that makes those meetings so special. R users are often not programmers by trade, but amateurs, who have a keen interest to extract stories and pictures from their data. And for that reason the discussions are often so engaging. Talking to people using R in social science, psychology, biology, pharma, energy, telcos, finance, insurance or actually statistics opens your mind and eyes. You realise that you are not alone, other people are weird as well. They have similar problems and challenges, but may use a different domain language and look at problems from a different angle. And this can be incredibly refreshing!

Anyhow, we agreed to meet again in about three months time. The pub was a great venue to socialise, yet a bit noisy for the talks. Hopefully we can use a room at the nearby university for the presentations next time. Promises were made already. We shall see. Günter was so kind to set up a mailing list to which you can sign up here. I will continue to use this blog to provide updates on the Cologne R user group in the future and set up a public calendar as well.

Talks

Many thanks to the speakers, who dared to give the first talks and had to improvise on the spot without a projector. Please drop me a line if you would like to speak at one of the next events.

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Reminder: Kölner R User Group meets on 30 March 2012

Venue: Sion em Keldenich, Weyertal 47, 50937 Cologne, Germany, 6 p.m., 30 March 2012,

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For more details and registration see the Kölner R User Group page.

Kölner R User Meeting 30 March 2012

Panorama of Cologne by Elke Wetzig. Source: Wikipedia, License: CC-BY-SA

Am 30. März 2012 möchte ich gerne das erste Kölner R Benutzer Treffen organisieren. Ich habe an den Treffen in London in den vergangen Jahren teilgenommen und hoffe auch in Köln Gleichgesinnte zu finden, die sich gerne bei einem Kölsch über R and das Leben unterhalten würden.

I would like to organise the first R user group meeting in Cologne, Germany, on 30 March 2012. In the past few years I have participated at the London R user groups and I hope to find also like-minded people in Cologne, who would like to catch up over a Kölsch on R and life in general.

Bitte geben Sie mir bescheid wenn Sie vorbei kommen möchten. Es erleichtert die Planung. Vorschläge für einen Vortrag werden gerne entgegengenommen.

Themen zu denen ich beisteuern kann sind zum Beispiel R in der Versicherungswelt, Daten Visualisierung, R im Zusammenspiel mit Datenbanken, LaTeX und MS Office.

Weitere Informationen werde ich später auf dieser Seite bereitstellen.

Please let me know if you would like to come along. It helps with the planning. I would very much appreciate suggestions for talks.

Topics on which I can contribute are for example R in the insurance industry, data visualisation, using R with data bases, LaTeX and MS Office.

I will provide further information and updates and the following page.