Basic data types

Introduction to Julia

James Fulton

Climate informatics researcher

Types of data

Integers are whole numbers

# This is stored as an integer
x_int = 1


# Print the type of x_int
println(typeof(x_int))

Int64

Floats are numbers with a decimal point

# This is stored as a float
x_float = 1.0


# Print the type of x_float
println(typeof(x_float))

Float64

Other basic data types

Booleans

x_bool = true # or false


# Print the type of x_bool
println(typeof(x_bool))

Bool

Strings

x_string = "Hello there"


# Print the type of x_string
println(typeof(x_string))

String

Must use "..."
Cannot use '...'

Other basic data types

Characters

x_char = 'A'


# Print the type of x_char
println(typeof(x_char))

Char

Cannot have character 'AB'
Only 'A' or 'B', etc.

Consequences of data types

# Bank balance as integer
balance = 100


# Interest rate as float
interest_rate = 1.05


new_balance = balance * interest_rate


println(new_balance)
println(typeof(new_balance))

105.0
Float64

# Bank balance as string
balance = "$100"

# Interest rate as string
interest_rate = "5%"

new_balance = balance * interest_rate


println(new_balance)
println(typeof(new_balance))

$1005%
String

Consequences of data types

# Bank balance as integer
balance = 100

# Interest rate as string
interest_rate = "5%"

new_balance = balance * interest_rate

ERROR: MethodError: 
no method matching *(::Int64, ::String)

Converting between types

# Convert the integer x to float y
x = 1

y = Float64(x)


println(typeof(y))

Float64

# Convert the float x to integer y
x = 1.0
y = Int64(x)


println(typeof(y))

Int64

Converting between types

# Convert the float x to integer y

x = 1.01

y = Int64(x)

ERROR: InexactError: Int64(1.01)

# Convert the float x to integer y
x = 1.0
y = Int64(x)


println(typeof(y))

Int64

Converting between types

# Convert the integer x to string y
x = 1
y = string(x) # y = "1"

println(typeof(y))

String

# Convert the string x to integer y
x = "1"
y = parse(Int64, x) 

println(typeof(y))

Int64

Converting between types

# Convert the integer x to string y
x = 1
y = string(x) # y = "1"

println(typeof(y))

String

# Convert the string x to float y
x = "1.0"

y = parse(Float64, x)


println(typeof(y))

Float64

Summary of conversions

Use typeof(x) to find the type of x
Convert between data types using:

From	To	Function
Integer	Float	`Float64(x)`
Float	Integer	`Int64(x)`
Integer or float	String	`string(x)`
String	Float	`parse(Float64, x)`
String	Integer	`parse(Int64, x)`

Let's practice!

Introduction to Julia