In a recent blog post I used something like this (for use in a call to optim()):
obj_fun_expr <- expression((x^4 + 4 * x^2 * y^2 - …

Let \(\rho_{XY}\) be the correlation between the stochastic variables \(X\) and \(Y\) and similarly for \(\rho_{XZ}\) and …

It is important to test software. One approach is unit-testing, and for R packages this can e.g. be done using testthat.
It is also …

Update Aug 10, 2019: I wrote a new blog post about the same as below but using a simulation approach.
Let \(\rho_{XY}\) be the …

As you may know, I am maintaining the Ryacas package (with online documentation) for doing symbolic mathematics (and other stuff) in R …

I am learning how to play piano. In that process, I needed charts with piano chords. I know it is good practise to construct the chords …

We (Søren Højsgaard and I) are preparing a new major release of Ryacas (GitHub). It will have a new interface to yacas that is thinner, …

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