Category: R

Linear mixed-effect models in R

Statistical models generally assume that All observations are independent from each other The distribution of the residuals follows $latex \mathcal{N}(0, \sigma^2)&s=1$, irrespective of the values taken by the dependent variable y When any of the two is not observed, more sophisticated modelling approaches are necessary. Let's consider two hypothetical¬†problems that violate the two respective assumptions, … Continue reading Linear mixed-effect models in R

Genome-wide association studies in R

This time I elaborate on a much more specific subject that will mostly concern biologists and geneticists. I will try my best to outline the approach as to ensure non-experts will still have a basic understanding. This tutorial illustrates the power of genome-wide association (GWA) studies by mapping the genetic determinants of cholesterol levels using … Continue reading Genome-wide association studies in R

Partial least squares in R

My last entry¬†introduces principal component analysis (PCA), one of many unsupervised learning tools. I concluded the post with a demonstration of principal component regression (PCR), which essentially is a ordinary least squares (OLS) fit using the first $latex k &s=1$ principal components (PCs) from the predictors. This brings about many advantages: There is virtually no … Continue reading Partial least squares in R