Variables

Introduction to Julia

James Fulton

Climate informatics researcher

Assigning variables

# Store the number 3 in the variable x
x = 3


# Print the variable
println(x)

double_x = 2*x
println(double_x)

Calculating with variables

# Distance run in meters
distance = 5000

# Time taken in minutes
time = 32.3


# Convert distance to miles and time to hours
distance_miles = distance/1609

time_hours = time/60


# Print speed in miles per hour
println(distance_miles/time_hours)

5.772483341575157

Calculating with variables

# Distance in meters
distance = 5000

# Time taken in minutes

time = 30.1


# Convert distance to miles and time to hours
distance_miles = distance/1609
time_hours = time/60

# Print speed in miles per hour
println(distance_miles/time_hours)

6.194392423019188

Naming variables

Variable names in previous example:

distance, time, distance_miles, time_hours

Must begin with letter [a-z] or [A-Z]
Or other unicode characters e.g. $\phi$, $\beta$, $\sigma$
Names of variables are in lower case

Words separated using by underscores _
Underscores can be omitted if still readable
- e.g. time_hours $\rightarrow$ timehours
Can use numbers after first letter
- x_times_2 is valid
- 2_times_x is not valid

More operations using variables

Operator	Operation	Example	Result
`+`	Add	`1+2`	`3`
`-`	Subtract	`4-2`	`2`
`*`	Multiply	`5*3`	`15`
`/`	Divide	`20/4`	`5`
`^`	Power	`2^3`	`8`

2^3 is the same as 2*2*2

speed = (distance/1609)/(time/60)
println(speed)

5.772483341575157

speed = distance/1609/time/60
println(speed)

0.0016034675948819882

Let's practice!

Introduction to Julia