Blog Archives

Using mutate from dplyr inside a function: getting around non-standard evaluation

September 23, 2015
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To edit or add columns to a data.frame, you can use mutate from the dplyr package: Here, dplyr uses non-standard evaluation in finding the contents for mpg and wt, knowing that it needs to look in the context of… See more ›

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Parsing a large amount of characters into a POSIXct object

September 22, 2015
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When trying to parse a large amount of datetime characters into POSXIct objects, it struck me that strftime and as.POSIXct where actually quite slow. When using the parsing functions from lubridate, these where a lot faster. The following benchmark shows… See more ›

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Tutorials freely available of course I taught: including ggplot2, dplyr and shiny

September 5, 2015
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I was asked to write a R course for a group of innovative companies in the North of the Netherlands. The group of 12 people was a mix of engineers and programmers, and the course aimed at giving them a… See more ›

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Data mining with R course in the Netherlands taught by Luis Torgo

January 29, 2014
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In the course of this year, Dr. Luis Torgo will teach a Data Mining with R course together with the DIKW Academy in Nieuwegein, The Netherlands. Dr. Torgo is an Associate Professor at the department of Computer Science at the… See more ›

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Vectorisation is your best friend: replacing many elements in a character vector

January 25, 2014
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As with any programming language, R allows you to tackle the same problem in many different ways or styles. These styles differ both in the amount of code, readability, and speed. In this post I want to illustrate this by… See more ›

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The performance of dplyr blows plyr out of the water

January 22, 2014
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Together with many other packages written by Hadley Wickham, plyr is a package that I use a lot for data processing. The syntax is clean, and it works great for breaking down larger data.frame‘s into smaller summaries. The greatest disadvantage… See more ›

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Bubble sorting in R, C++ and Julia: code improvements and the R compiler

December 28, 2013
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In the past few months I have written posts about implementing the bubble sort algorithm in different languages. In the mean while I have gotten some feedback and suggestions regarding improvements to the implementation I made, see the end of… See more ›

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Parallel processing with short jobs only increases the run time

December 27, 2013
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Parallel processing with short jobs only increases the run time

Parallel processing has become much more important over the years as multi-core processors have become common place. From version 02.14 onwards, parallel processing has become part of the standard R installation in the form of the parallel package. This package… See more ›

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Julia is lightning fast: bubble sort revisited

December 26, 2013
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I had heard the name of the new technical computing language Julia buzzing around for some time already. Now during Christmas I had some time on my hands, and implemented the bubble sort algorithm that I have already posted about… See more ›

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Much more efficient bubble sort in R using the Rcpp and inline packages

May 14, 2013
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Recently I wrote a blogpost showing the implementation of a simple bubble sort algorithm in pure R code. The downside of that implementation was that is was awfully slow. And by slow, I mean really slow, as in “a 100… See more ›

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