Blog Archives

Simulating average height of a random binary search tree

January 22, 2012
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Simulating average height of a random binary search tree

Recently on Stack Overflow I have found a discussion on Average height of a binary search tree. The problem has been solved analytically, see for example Reed (2003). However, I was intrigued by one of the answers that presented a simulation ...

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Exercise in grImport

January 13, 2012
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Exercise in grImport

Last week I used grImport for the first time. I decided to try perform another exercise using it. The task was to add voivodeship division of Poland.Standard R maps do not contain such a division. I have found it on r-forge in package  m...

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Coat of arms of Poland challenge

January 5, 2012
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Coat of arms of Poland challenge

Last week I have experimented with coloring map of Poland in national colors. Vaidotas Zemlys improved on my effort by adding colors to map of Lithuania and posted a challenge to also add coat of arms to the plot. This proved to be a nice exe...

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Color map of Poland for the New Year

December 31, 2011
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Color map of Poland for the New Year

To celebrate the New Year I decided to plot map of Poland in our national colors.It was not so difficult using maps  package. Here is the result:and the code I used to generate it:library(maps)x.mid <- function(x1, x2, y1, y2, y.mid) {&nbs...

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Programming traps when using "sample"

December 23, 2011
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Programming traps when using "sample"

Standard sample function works differently when it gets single element integer vector as opposed to longer vectors. This can lead to unexpected bugs in R code.Several times I had a problem with code similar to one given here:for (i in 1:4) {&...

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Optimal regularization for smoothing splines

December 16, 2011
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Optimal regularization for smoothing splines

In smooth.spline procedure one can use df or spar parameter to control smoothing level. Usually they are not set manually but recently I was asked a question which one of them is a better measure of regularizatio...

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Stability of classification trees

December 9, 2011
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Stability of classification trees

Classification trees are known to be unstable with respect to training data. Recently I have read an article on stability of classification trees by Briand et al. (2009). They propose a quantitative similarity measure between two trees. The method is i...

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Comparing model selection methods

December 2, 2011
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Comparing model selection methods

The standard textbook analysis of different model selection methods, like cross-validation or validation sample, focus on their ability to estimate in-sample, conditional or expected test error. However, the other interesting question is to compare the...

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Working with isTRUE

November 25, 2011
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Working with isTRUE

This week I was running computations transforming some input files into output files. The problem was that it was a repeated process. If new input files were generated or old ones were updated I needed to calculate new output files. The transformation ...

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randu dataset, part 2

November 19, 2011
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randu dataset, part 2

In my last post I have plotted randu dataset to show that all its points lie on 15 parallel planes. But I was not fully satified with the solution and decided to show this numerically.It can be done in four steps:identifying four points lying...

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