PROJECT LAUNCH
New Project
File >New Project > New Directory
New R script

File > New File > R Script

Where am I? 
# Show current working directory
getwd() 
# Set new working directory
setwd("C:/my-data-folder")
Install new packages 
install.packages("readr")
library(readr)
STORE VALUES 
# Use the left-arrow
age <- 7.2

# Text goes in quotes
porg <- "Sunshine"

# Multiple values go inside c()
droids <- c("BB8", "R2D2", "C-3PO")

# Copy an object
my_droids <- droids

# Avoid numbers, spaces, & symbols
3-droids* <- "error_invalid_name"
READ DATA

Text files (.csv, .txt, .tab)

library(readr)
porgs <- read_csv("txt_file.csv")

Excel files (.xlsx, .xls)

library(readxl)
porgs <- read_excel("Excel_file.xlsx")
CLEAN NAMES 
# Simplify all column names
library(janitor)
porgs <- clean_names(porgs)

# Assign new names manually
library(dplyr)
# Put new name on left: new_name = oldName
rename(porgs, mass_kg = massKG)
DESCRIBE DATA 
library(dplyr)
nrow(porgs)
names(porgs)
summary(porgs)
glimpse(porgs)
class(porgs)
# View unique column values
distinct(porgs, age)
## 5 6 11 12 3
ADD COLUMNS 
library(dplyr)

# Add home planet column
mutate(porgs, 
       planet = "Earth")
# Add new calculated column
mutate(porgs, 
       growth = height / age)
PLOTS
Scatterplot 
library(ggplot2)

ggplot(porgs, aes(x = name, y = age)) +
  geom_point(size = 8, color = "hotpink")
Add titles & lines 
ggplot(porgs, aes(x = name, y = age)) +
  geom_point(size = 8, color = "hotpink") +
  geom_hline(yintercept = 5, 
             linetype   = "dashed") +
  labs(title    = "Porgs",
       subtitle = "Sampled on planet Ahch-To", 
       caption  = "data from New Republic")
Facet by group 
ggplot(porgs, aes(x = name, y = age)) +
  geom_point(aes(color = color), size = 8) +
  facet_wrap(~color) +
  scale_color_manual(values = c("gray", "yellow")) + 
  theme_dark()



FILTER 
library(dplyr)
# Keep only Porgs older than 3
filter(porgs, age > 3)
# Keep rows with name Jumpity
filter(porgs, name == "Jumpity")
# Keep Porgs named Jumpity OR Chicken
filter(porgs, name %in% c("Jumpity", "Chicken"))
SUMMARIZE 
library(dplyr)
# Summarize the age for the entire table
summarize(porgs, avg_age = mean(age))
# Summarize the age for each color group
group_by(porgs, color) %>%
    summarize(avg_age = mean(age))
COMPARISONS
Symbol Comparison
> greater than
>= greater than or equal to
< less than
<= less than or equal to
== equal to
!= NOT equal to
%in% is value X in list: X %in% c(1,3,5)
is.na(...) is the value missing?