Create dataframe

Create variables

## i. name
names <- c("Ada","Robert","Mia")

## ii. age
ages <- c(20,21,22)


## iii. Factor, so that you can add levels that not exist in the data
year <- c("Freshman","Sophomore","Junior")
year <- factor(year, levels=c("Freshman","Sophomore",
                              "Junior","Senior"))

Create dataframe

students <- data.frame(names,ages,year)

Query a dataframe

students$names

Set working dictory

get working dicrectory

getwd()

set working directory

setwd()

or go to “session” and set working directory

or build R file in the directory you want to work in