# welcome to week 3!

# vectors!

x <- 5
x
weight_g <- c(50, 60, 65, 82)

animals <- c("mouse", "rat", "dog")

# class tells us the data type in a vector
class(weight_g)
class(animals)

# str for structure
str(weight_g)
str(animals)

# we can modify vectors with the c() function


c(50, 60, 65, 82, 90)

weight_g <- c(weight_g, 90)

weight_g <- c(30, weight_g)

weight_g


2L

x <- 1:10
class(x)

# coercion challenge

num_char <- c(1, 2, 3, "a")
class(num_char)
num_char

num_logical <- c(1, 2, 3, TRUE)
class(num_logical)
num_logical

char_logical <- c("a", "b", "c", TRUE)
class(char_logical)
char_logical

tricky <- c(1, 2, 3, "4")
class(tricky)

# challenge 2
combined_logical <- c(num_logical, char_logical)
combined_logical

class(combined_logical)


# subsetting vectors

animals <- c("mouse", "rat", "dog", "cat")
animals[2]

animals[c(3,2)]

animals[c(3, 2, 4, 1, 2, 1)]

animals[0]

# conditional subsetting

weight_g <- c(21, 34, 39, 54, 55)
weight_g[c(TRUE, FALSE, TRUE, TRUE, FALSE)]


weight_g > 50

weight_g[weight_g > 50]

# multiple operations at once
weight_g[weight_g < 30 | weight_g > 50]

weight_g[weight_g >= 30 & weight_g == 21]

animals

animals[animals == "cat" | animals == "rat"]

animals %in% c("mouse", "rat")

animals[animals %in% c("mouse", "rat")]

"four" > "five"
"six" > "four"

"eight" > "six"
"alpha" > "beta"

"dog" > "cat"


# vector math

x <- 1:10

x + 3

x * 10

y <- 100:109

x + y
x
y

z <- 1:2

x
z
x + z

z <- 1:3

x + z

a <- x + z
a
x
z

str(x)
str(z)

length(x)
length(z)

# recycling with conditional subsetting
x[c(TRUE, FALSE)]

x[c(TRUE, FALSE, FALSE)]

#Working with Missing Data

#In R missing are represented as NAs

heights <- c(2, 4, 4, NA, 6)

mean(heights)
max(heights)

#na.rm = NA Remove 

mean(heights, na.rm = TRUE)

max(heights, na.rm = TRUE)

class(heights) #numeric, NA is not a character, R views it as a number (sort of)
heights

#is.na = Is it a NA? 

is.na(heights)

#! = is not 

!is.na(heights)

heights[!is.na(heights)]

heights[is.na(heights)]

#complete.cases = extracting all the elements that are complete cases (are not NAs)

heights[complete.cases(heights)]

#CHALLENGE!

heights <- c(63, 69, 60, 65, NA, 68, 61, 70, 61, 59, 64, 69, 63, 63, NA, 72, 65, 64, 70, 63, 65)

#remove the NAs

heights2 <- heights[complete.cases(heights)]
heights2

median(heights2)

#longer than 67 inches 

length(heights2[heights2 > 67])

(heights2[heights2 > 67])

#Factors are a bit funky 

sex <- factor(c("male", "female", "female", "male"))
class(sex)
typeof(sex)

levels(sex)

nlevels(sex)

#specify the order of the levels 

sex <- factor(sex, levels = c("male", "female"))

sex

#making factors into characters 

sex_ch <- as.character(sex)