Some recipes will need the Eigen linear algebra template library, version 3.3 or later. If your package manager does not provide Eigen, you can install it from the online source archive (http://eigen.tuxfamily.org). For example, on GNU/Linux and macOS, you can install Eigen to the directory $HOME/Deps/eigen, as follows:
$ eigen_version="3.3.4"$ mkdir -p eigen$ curl -Ls http://bitbucket.org/eigen/eigen/get/${eigen_version}.tar.gz | tar -xz -C eigen --strip-components=1$ cd eigen$ cmake -H. -Bbuild_eigen -DCMAKE_INSTALL_PREFIX="$HOME/Deps/eigen" &> /dev/null$ cmake --build build_eigen -- install &> /dev/null
