Efficient Fitting of Linear and Generalized Linear Models by using just base R. As an alternative to lm() and glm(), this package provides elm() and eglm(), with a significant speedup when the number of observations is larger than the number of parameters to estimate. The speed gains are obtained by reducing the NxP model matrix to a PxP matrix, and the best computational performance is obtained when R is linked against 'OpenBLAS', 'Intel MKL' or other optimized 'BLAS' library. This implementation aims at being compatible with 'broom' and 'sandwich' packages for summary statistics and clustering by providing S3 methods.