https://blog.xijiang.org/tags/random-regression/ Recent content in Random Regression on Breeding and genetics Hugo en-us Mon, 01 Jun 2026 09:40:48 +0200 https://blog.xijiang.org/posts/random-regression-covariates-softwares-n-model-evaluation/ Mon, 01 Jun 2026 09:40:48 +0200 https://blog.xijiang.org/posts/random-regression-covariates-softwares-n-model-evaluation/ <p>This post captures key concepts, comparisons, and design criteria for random regression models (RRMs) used to analyze longitudinal phenotypic and genomic data.</p> <hr> <h2 id="1-comparison-of-covariate-functions-for-random-regression">1. Comparison of Covariate Functions for Random Regression</h2> <p>When modeling longitudinal trajectories (such as milk yield or growth curves), the time covariate must be modeled using mathematical functions. The table below compares the most common choices:</p> <h3 id="11-legendre-polynomials-orthogonal-polynomials">1.1 Legendre Polynomials (Orthogonal Polynomials)</h3> <p>Traditionally the most popular choice in animal breeding (Kirkpatrick &amp; Heckman, 1989; Meyer, 1998). Time is scaled to the interval $[-1, 1]$ and orthogonal polynomial terms are evaluated.</p>