Joining data

Data Manipulation in Julia

Katerina Zahradova

Instructor

Why we join

More information not already included in the dataset
Datasets from different sources
...

Left join

Left Join

Left join in practice

More info about joins here

# Left join on chocolates and chocolate_companies, using company column
leftjoin(chocolates, chocolate_companies, on = :company)

¹ https://dataframes.juliadata.org/stable/man/joins/

Joining on columns with different names

# Left join on chocolates and chocolate_companies, using company and company_name
leftjoin(chocolates, chocolate_companies, on = :company => :company_name)

Joining on multiple columns

# Left join on chocolates and chocolate_companies
# using company and company_location columns
leftjoin(chocolates, chocolate_companies, 
                on = [:company => :company, :company_location => :company_location])

Cheat sheet

leftjoin(left, right, on = :col):

returns all rows and columns from left, along with those rows of right that have a matching value in col with left

leftjoin(left, right, on = :col_left => :col_right):

left join when the columns don't have the same name

leftjoin(left, right, on = [:c1_l => :c1_r, ...]):

left join on multiple columns

Let's practice!

Data Manipulation in Julia