Markov chains is a very interesting and powerful tool. Especially for parents. Because if you think about it quickly, most of the games our kids are playing at are Markovian. For instance, snakes and ladders... It is extremely easy to write down th...
Last time we looked at the Matrix package and dug a little into the chol(), Cholesky Decomposition, function. I noted that often in finance we do not have a positive definite (PD) matrix. The chol() function in both the Base and Matrix...
Once you’re comfortable with 2-arrays and 2-matrices, you can move up a dimension or two, to 4-arrays or 4-tensors. You can move up to a 3-array / 3-tensor just by imagining a matrix which “extends back into the blackboard”. Like a 5 × 5 ma...
![Le Monde puzzle [#738]](http://feeds.wordpress.com/1.0/comments/xianblog.wordpress.com/11990/)
The Friday puzzle in Le Monde this week is about “friendly perfect squares”, namely perfect squares x2>10 and y2>10 with the same number of digits and such that, when drifting all digits of x2 by the same value a (modulo 10), one recovers y2. For instance, 121 is “friend” with 676. Here is my...
Scatterplots can get very hard to interpret when displaying large datasets, as points inevitably overplot and can't be individually discerned. A number of approaches have been crafted to help with this problem. One approach uses binning. This approa...
Here's an example how to conveniently summarize data with the cast function (package reshape). By the way you see how this could be done "in-conveniently" by hand. You also see how a for-loop works and how a matrix is constructed and fill...
As far as I can tell, R doesn’t have a function for building block diagonal matrices so as I needed one, I’ve coded it myself. It might save someone some time. Example: Let m1 and m2 two square matrices. Selec … Continue reading →
With the distance matrix found in previous tutorial, we can use various techniques of cluster analysis for relationship discovery. For example, for the data set mtcars, we can use the hclust method with the distance matrix and plot a dendrogram that ...
A contour plot is a simple way to plot a surface in two dimensions. Lines with a constant Z value are plotted on the X-Y plane.Typical uses include weather maps displaying "isobars" (lines of constant pressure), and maps displaying lines of constant e...
mat.sort <- function(mat,n) { mat),] <- mat return(mat) } a <- matrix(rnorm(100),ncol=10) mat.sort(a,1)
Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).
