You newly install R program when all of your packages are lost.

start_up.R

# List of useful packages
pkg <- c("tidyr", "dplyr", "ggplot2", "knitr", "rmarkdown")

# Check if packages are not installed and assign the
# names of the uninstalled packages to the variable new.pkg
new.pkg <- pkg[!(pkg %in% installed.packages())]

# If there are any packages in the list that aren't installed,
# install them
if (length(new.pkg)) {
  install.packages(new.pkg, repos = "http://cran.rstudio.com")
}