# Generalized inverse of a symmetric matrix

I have always found the common definition of the generalized inverse of a matrix quite unsatisfactory, because it is usually defined by a mere property, $A A^{-} A = A$, which does not really give intuition on when such a matrix exists or on how it can be constructed, etc… But recently, I came across a much more satisfactory definition for the case of symmetric (or more general, normal) matrices.

# Logistic regression with categorical data in Ruby

I had some fun analysing the shelter animal data from kaggle using the Ruby gems `daru`

for data wrangling and `statsample-glm`

for model fitting. In this blog post, I want to demonstrate that data wrangling and statistical modeling is not an area of absolute predominance of Python and R, but that it is possible in Ruby too (though, currently to a much lesser extent).