In which CRAN mirror is the quadprog package available?
The quadprog package is available on all CRAN mirrors, but it requires the latest R version: R 3.6.0 (released on Apr 26, 2019), see also https://cran.r-project.org/web/packages/quadprog/index.html

&gt; quadprog: Functions to Solve Quadratic Programming Problems
&gt; 
&gt; This package contains routines and documentation for solving quadratic
&gt; programming problems.
&gt; Version:    1.5-6
&gt; Depends:    R (≥ 3.6.0)
&gt; Published:  2019-04-26