packages <- c("tidyverse")
packages <- lapply(packages, FUN = function(x) {
if(!require(x, character.only = TRUE)) {
install.packages(x)
library(x, character.only = TRUE)}})
df <- diamonds
head(df, 5)
tail(df, 5)
df <- df[order(df$carat),]
df <- df[order(df$carat, df$price),]
df <- df[order(df$carat, -df$price),]
df[,]
df[1,]
df[1:2,]
df[ c(1,3), ]
df[1, 2:3]
df[1:2, 2:3]
df[, 1]
df[,c(1,3)]