
A rudimentary first linear mixed model fit
During the last two weeks I made some progress on my Google Summer of Code project. The Ruby gem is now capable of fitting linear mixed models. In this short blog post I want to give an example, and compare the results I get in Ruby to those obtained by
READ MORElme4
in R. 
Dissecting lme4's lmer function. Part 3.
This is the final part of my analysis of the function
READ MORElmer
, which is used to fit linear mixed models in the R packagelme4
. In two previous blog posts, we have seen the general layout of the functionlmer
, the dealings with the R model formula, and the setting up of the objective function for the optimization (see part 1 and part 2). 
Dissecting lme4's lmer function. Part 2.
Last time I started to analyze the function
READ MORElmer
that is used to fit linear mixed models in the R packagelme4
. I have delineated the general steps taken bylmer
, and looked at the employed formula module in more detail. The formula module evaluates the provided R model formula to model matrices, vectors and parameters. The next step is to use these to define the objective function that needs to be minimized, which is the profiled deviance or the profiled REML criterion in this case. The objective function is returned by the functionmkLmerDevfun
which is dissected in what follows. 
Dissecting lme4's lmer function. Part 1.
This blog posts marks the start of my Google Summer of Code project with the Ruby Science Foundation, where I will develop mixed linear models software for Ruby. As a preparation for my GSoC project, I will dedicate a couple of blog posts to a meticulous analysis of
READ MORElme4
code (so that I can steal all the ideas from it!). 
Solve twopoint boundary value problems in Ruby with spitzy
A few days ago I programmed a numerical method for the solution for twopoint boundary value problems, and today I discovered that I can use MathJax to display mathematical formulas in here (although there are some inconveniences related to the use of underscores). So, here goes another blog post!
READ MORE 
Solve ODEs in Ruby with spitzy
Over the weekend I have written a couple of numerical solvers for onedimensional initial value problems in Ruby, and added them to my project spitzy.
READ MORE 
Solve an advection equation in Ruby with spitzy
A couple of days ago I started working on a collection of numerical methods for differential equations, wirtten in pure Ruby (I have conviced the professor of my numerical DE class that that`s a good idea for my final project in said class).
READ MORE 
NMatrix column permutations
Recently I got surprised by the behaviour of
READ MORE#permute_columns
in the Ruby gem NMatrix. 
Hello World!
Hello World!
READ MORE
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