### Davis R Users Group: Teaching R Live Code
### https://tinyurl.com/teachingR
### https://tinyurl.com/teachingRnew # this link goes to raw script, without Dropbox stuff to slow down browser

### FYI: This is a frequently updated R script used for "live-coding" while teaching. Contents may be removed/altered/changed and saved to the Davis R Users Group website: https://d-rug.github.io/ 

# for today's lesson, we'll be going Halloween themed!
# click the following link to download the candy data
# https://tinyurl.com/CandySalesData

# if we need it, we might also look at some ecological data (boring, I know): https://tinyurl.com/y36xgftg

# hello everyone, happy halloween

candy <- read.csv(file = "data/cleaned/candy_sales_cleaned.csv")

# head() function to look at the top of our data frame
head(candy)

# View() to look at the whole thing
View(candy)

my_vector <- c(1, 3, "cat")
my_vector

# str() for structure
str(candy)

dim(candy)
nrow(candy)
ncol(candy)

# top or bottom of the dataframe
head(candy)
tail(candy)

# names of your columns and rows
names(candy) # column names
rownames(candy)

# summary() to give a quick summary of the data
summary(candy)

# tons of ways to subset a dataframe
# this will give us the first row and first column of our data
candy[1,1]

# first element in the 5th column
candy[1,5]

candy[1,4]

# whole 3rd column
candy[,3]
class(candy[,3])
class(candy)
# this method gets us a whole column as a vector

# this method gets us the 2nd column as a dataframe
candy[2]
class(candy[2])

# first 3 entries in the 3rd column (as a vector)
candy[1:3,3]

# let's pull out one whole row
candy[5,]

# let's copy what the head() function does
candy[1:6,]

# let's leave some stuff out
candy[,-1]

# leave some rows out
candy[-c(1:5),]

# using column names to pull out data

# this one gives us a dataframe back
candy["lbs_sold"]

# this one gives us a vector
candy[,"lbs_sold"]

# we need to go deeper: gives us back a vector
candy[["lbs_sold"]]

# dollar sign subset to pull out a column (another one as a vector)
candy$rank

# let's get back to logical subsetting

candy$rank < 3
candy[candy$rank < 3,]

# factor time

chocolate <- factor(c("yes", "no", "no", "yes", "yes"))
chocolate

levels(chocolate)
levels(candy$name)

# as.character() to convert factors
as.character(chocolate)

# what happens if we ask for a factor as numeric?
as.numeric(chocolate)

# factor where levels are numbers
years <- factor(c(1998, 1999, 2000))
years
as.numeric(years)
as.character(years)
as.numeric(as.character(years))

read.csv(stringsAsFactors = F)