From RStudio's CRAN Mirror http://cran-logs.rstudio.com/
packageLog(packages = NULL, date = Sys.Date() - 1, filter = FALSE,
memoization = TRUE)
Character. Vector of package name(s).
Character. Date.
Logical or Numeric. If Logical, TRUE filters out downloads less than 1000 bytes. If Numeric, a positive value (bytes) sets the minimum download size to consider; a negative value sets the maximum download size to consider.
Logical. Use memoization when downloading logs.
An R data frame.