326 search results for "evaluation"

Genetic algorithms: a simple R example

August 1, 2012
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Genetic algorithms: a simple R example

Genetic algorithm is a search heuristic. GAs can generate a vast number of possible model solutions and use these to evolve towards an approximation of the best solution of the model. Hereby it mimics evolution in nature. GA generates a population, the individuals in this population (often called chromosomes) have a given state. Once the population is generated, the state of these individuals is evaluated...

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Bio7 1.6 for Windows and Linux released!

August 1, 2012
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Bio7 1.6 for Windows and Linux released!

01.08.2012 Finally i released a new version of Bio7 with many improvements and new features. Updated tutorials are available, too. The new Bio7 1.6 release can be downloaded here. Please also download the examples *.zip file from the sourceforge website which contains new examples for Bio7 1.6 (e.g. an example to cluster an image folder with

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Edge Prediction in a Social Graph: My Solution to Facebook’s User Recommendation Contest on Kaggle

July 31, 2012
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Edge Prediction in a Social Graph: My Solution to Facebook’s User Recommendation Contest on Kaggle

A couple weeks ago, Facebook launched a link prediction contest on Kaggle, with the goal of recommending missing edges in a social graph. I love investigating social networks, so I dug around a little, and since I did well enough to score one of the coveted prizes, I’ll share my approach here. (For some background, the contest provided...

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Forecasting the Olympics

July 30, 2012
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Forecasting sporting events is a growing research area. The International Journal of Forecasting even had a special issue on sports forecasting a couple of years ago. The London 2012 Olympics has attracted a few forecasters trying to predict medal counts, world records, etc. Here are some of the articles I’ve seen. Which Olympic records get shattered?, Nate Silver, New...

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Changing function scope in GNU R example

July 26, 2012
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In my last post I have discussed how to work around GNU R scoping rules using environment function. This time let us look at a practical example using recode function from car package.First let us look at how&nbs...

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XLConnect 0.2-0

July 23, 2012
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XLConnect 0.2-0

Mirai Solutions GmbH (http://www.mirai-solutions.com) is very pleased to announce the release of XLConnect 0.2-0, which can be found at CRAN. As one of the updates, XLConnect has moved to the newest release of Apache POI: 3.8. Also, the lazy evaluation … Continue reading →

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Announcing eeptools

July 22, 2012
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The LDS_TOOLS package for R has been replaced by the new eeptools package. I am renaming the package for a number of reasons. First, LDS is a technical industry term in education that stands for Longitudinal Data Systems, which is not commonly known an...

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Emulating dynamic scoping in GNU R

July 21, 2012
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By design GNU R uses lexical scoping. Fortunately it allows for at least two ways to simulate dynamic scoping.Let us start with the example code and next analyze it:x <- "global"f1 <- function() cat("f1:", x, "\n")f2 <- function() cat("f2:", e...

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Automatic Hyperparameter Tuning Methods

July 20, 2012
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At MSR this week, we had two very good talks on algorithmic methods for tuning the hyperparameters of machine learning models. Selecting appropriate settings for hyperparameters is a constant problem in machine learning, which is somewhat surprising given how much expertise the machine learning community has in optimization theory. I suspect there’s interesting psychological and

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A weighting function for ‘nls’ / ‘nlsLM’

July 19, 2012
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A weighting function for ‘nls’ / ‘nlsLM’

Standard nonlinear regression assumes homoscedastic data, that is, all response values are distributed normally.  In case of heteroscedastic data (i.e. when the variance is dependent on the magnitude of the data), weighting the fit is essential. In nls (or nlsLM of the minpack.lm package), weighting can be conducted by two different methods: 1) by supplying

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