I often use constrOptim to quickly solve nonlinear optimization problems. constrOptim works well as a general tool to tackle constrained problems like\[\min_{Ax -b \geq0} f(x)\]  There are many other options and packages for specific problems but constrOptim is likely to be the first choice when little is ... [Read more...]

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I engage with the Stack[Overflow|Exchange] community quite a bit and was super-happy @treycausey made the Stack Overflow #rstats bot (@StackOverflowR) since I’m also on Twitter alot (mostly hanging out in #rstats these days). However, #rstats questions exist in other Stack watering holes, like the Geographic Information Systems ... [Read more...]

Something missing In my last post I developed a new scale transformation for R using the approach and platform from the {ggplot2} and {scales}. I implemented a method proposed in 1980 by John and Draper that does some of the job of a logarithmic transform in reducing the dominance on the ... [Read more...]

In two previous posts (Predicting Titanic deaths on Kaggle IV: random forest revisited, Predicting Titanic deaths on Kaggle) I was unable to make random forest predict as well as boosting. Hence when I read about an alternative implementation; ranger I took the opportunity to check if with ranger I could ... [Read more...]

In two previous posts (Predicting Titanic deaths on Kaggle IV: random forest revisited, Predicting Titanic deaths on Kaggle) I was unable to make random forest predict as well as boosting. Hence when I read about an alternative implementation; ranger&n... [Read more...]

In fisheries analysis it is fairly common to compute the cumulative sum of values in a vector – i.e., all values before and including the current position in the vector. For example, the third value in the cumulative sum would be the sum of the first, second, and third values ... [Read more...]

A second maintenance release 0.1.4 of our RcppDE package, following on the heels of the recent 0.1.3. release arrived on CRAN today. RcppDE is a "port" of DEoptim, a popular package for derivative-free optimisation using differential optimization, to C++. By using RcppArmadillo, the code becomes a lot shorter and more legible. This ... [Read more...]

Clay tablet YBC 7289 with an overlay to emphasize the markings on its surface. The cuneiform inscriptions demonstrate the derivation of the square root of 2 … in sexagesimal (base-60) via Paul Murrell the tablet has been dated to sometime between 1800 BC and 1600 BC. Little is known of its rediscovery, except that it ... [Read more...]

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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 › [Read more...]

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A FSA user recently asked me if there was a way to see and work with the age comparison results for individual fish. In particular, this user wanted to identify each fish for which the individual CV values from comparing two independent age estimates was greater than 10. It turns out ... [Read more...]

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Revolution R Open, the enhanced open source R distribution from Revolution Analytics and Microsoft, is now available for download. This update brings multi-threaded performance to the latest update to the R engine from the R Core Group, which includes several improvements and bug fixes. Significant amongst these is default support ... [Read more...]

In data analysis it happens sometimes that it is neccesary to use weights. Contexts that come to mind include: Analysis of data from complex surveys, e.g. stratified samples. Sample inclusion probabilities might have been unequal and thus observations from different strata should have different weights. Application of propensity score ... [Read more...]