I would like to get the slope of a linear regression fit for 1M separate data sets (1M * 50 rows for data.frame, or 1M * 50 for array). Now I am using the
Yes there are:
R itself has
lm.fit() which is more bare-bones: no formula notation, much simpler result set
several of our Rcpp-related packages have
fastLm() implementations: RcppArmadillo, RcppEigen, RcppGSL.
We have described
fastLm() in a number of blog posts and presentations. If you want it in the fastest way, do not use the formula interface: parsing the formula and preparing the model matrix takes more time than the actual regression.
That said, if you are regressing a single vector on a single vector you can simplify this as no matrix package is needed.