There are two limitations of Watts-Strogatz network generator in igraph package: (1) it works only for undirected graphs and (2) rewiring algorithm can produce loops or multiple edges.You can use simplify function of such a graph, but then number of ed...
This week I reimplemented part of Conic Sections 1 model from NetLogo. In the model turtles seek to to be in target distance from center.My code takes only one center point, so only circles can be obtained. Apart from turtle location plot giv...
While preparing for the new semester I have started reimplementing standard NetLogo examples in R. The first is Fire model.The simulation in R is presented here:# Forest matrix trees encoding:# 3 – green, 2 – burning, 1 – burnt, 0 – no treesimu...
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 ...
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...
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...
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...
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) {&...
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...
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...
Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).