[R] How to get the names of all the packages that depend on a give package?

[thmsfuller066 at gmail.com]

Dear All,

I want to check what packages depends on a given package. For example,
glmnet depends on Matrix. I want get the names of all the packages
that depend on Matrix on CRAN. Is there a way to do so? Thanks!

> library(glmnet)
Loading required package: Matrix
Loading required package: lattice

-- 
Tom