Many thanks to Gregory Gundersen for the blog theme.
The Kullback-Leibler Divergence
17 February 2025
1
Cholesky Decomposition of an Inverse Covariance Matrix
15 January 2025
Interpreting the Cholesky factor of a Gaussian precision matrix.
2The Reversed Cholesky Decomposition
14 January 2025
Cholesky-like decomposition with upper-triangular matrices.
3Interpreting the inverse covariance matrix for Gaussian distributions.
4Gaussian Kernel Hyperparameters
26 December 2024
Interpreting and optimizing the lengthscale and marginal variance parameters of a Gaussian covariance function.
5Cholesky Decomposition of a Covariance Matrix
25 December 2024
Interpreting the Cholesky factor of a Gaussian covariance matrix.
6Combining Samples From Non-mixing MCMC Chains
12 December 2024
7
Regularized Least Squares with Singular Prior
03 December 2024
Solving the regularized least squares optimization problem when the prior covariance matrix is not positive definite.
803 November 2024
Combining and splitting models in a Bayesian framework.
9Ensemble Kalman Methodology for Inverse Problems
05 October 2024
Particle-based Kalman methods for the approximate solution of Bayesian inverse problems.
1028 September 2024
Motivated by Bayesian inference, I introduce the pseudo-marginal approach to MCMC and then discuss why is works from a more generic perspective.
1130 July 2024
I introduce the ensemble Kalman filter as a Monte Carlo approximation to the Kalman filter in the linear Gaussian state space setting, then discuss how is applied as an approximation even when these assumptions don't hold.
12Linear Gaussian Inverse Problems
03 July 2024
Derivations and discussion of linear Gaussian inverse problems.
1327 June 2024
Introduction and basic properties, kernel ridge regression, Gaussian processes.
14Basis Expansions for Black-Box Function Emulation
25 June 2024
A discussion of the popular output dimensionality strategy for emulating multi-output functions.
15A Few Different Adaptive Metropolis Schemes
10 June 2024
Adaptively updating a Gaussian proposal covariance for Random Walk Metropolis-Hastings samplers.
1630 May 2024
An introduction to dimensionality reduction via active subspaces.
17Gaussian measures in finite dimensions; i.e., multivariate Gaussians/Gaussian vectors.
18Gaussian Measures, Part 1 - The Univariate Case
16 May 2024
A brief introduction to Gaussian measures in one dimension, serving to provide the setup for an extension to multiple, and eventually infinite, dimensions.
19An Introduction to Scattered Data Approximation
24 March 2024
I summarize the first chapter of Holger Wendland's book "Scattered Data Approximation", which I augment with some background on polynomial interpolation and splines.
20Generalizing the Outer Product to Hilbert Space
18 March 2024
I briefly discuss how the outer product, familiar in Euclidean space, can be viewed as a linear operator which can readily be generalized to Hilbert space.
21Gaussian Conditioning under Linear Transformations
06 March 2024
I derive generalizations of the standard Gaussian conditioning identities whereby components of the Gaussian vector are subject to linear maps, and highlight applications to Gaussian processes.
22Approximating Nonlinear Functions of Gaussians, Part I - Linearized Kalman Filter Extensions
15 February 2024
I discuss the generic problem of approximating the distribution resulting from a non-linear transformation of a Gaussian random variable, and then show how this leads to extensions of the Kalman filter which yield approximate filtering algorithms in the non-linear setting.
2315 February 2024
I discuss the Kalman filter from both the probabilistic and optimization perspectives, and provide multiple derivations of the Kalman update.
24An Introduction to Bayesian Filtering and Smoothing
29 January 2024
I provide an overview of the general framework for statistical filtering, viewed from the Bayesian perspective.
25The Measure-Theoretic Context of Bayes' Rule
28 January 2024
I describe Bayes' rule in a measure-theoretic context, explain how it can be viewed as a non-linear operator on probability measures, and detail applications to Bayesian inverse problems.
26Gaussian Process Priors, Specification and Parameter Estimation
11 January 2024
A deep dive into hyperparameter specifications for GP mean and covariance functions, including both frequentist and Bayesian methods for hyperparameter estimation.
27Deriving the Metropolis-Hastings Update from the Transition Kernel
31 December 2023
Given only the Metropolis-Hastings transition kernel, I show how to recover the Metropolis-Hastings update rule.
2815 December 2023
I derive the PCA decomposition from both a minimum reconstruction error and maximum variance perspective. I also discuss a statistical interpretation of PCA.
29