# 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")
 }

# Último paquete sin el cual no funciona
 if (!require("tm")) install.packages("tm")