Eliminare e spostare colonne

Manipolazione dei dati in Julia

Katerina Zahradova

Instructor

Come selezionare quasi tutte le colonne

# Seleziona tutte le colonne di chocolates tranne review_date
select(chocolates, :company, :bean_origin, :REF, :cocoa,
        :company_location, :ratings, :bean_type, :bean_location)

ArgumentError: column name "ratings" not found in the data frame; 
    existing most similar names are: "rating"
...

Operatore Not()

# Seleziona tutte le colonne di chocolates tranne review_date
select(chocolates, Not(:review_date))

1795×9 DataFrame 
Row company  bean_origin REF   cocoa   company_location rating  bean_type bean_location
    String   String      Int64 Float64 String31         Float64 String31? String31?
______________________________________________________________________________________
1   A. Morin Agua Grande 1876  63.0    France           3.75    Sao Tome
...

Insidie di select() e not()

# Eliminare la stessa colonna due volte
select!(chocolates, Not(:review_date))

# Qualche riga di codice dopo...

select(chocolates, Not(:review_date))

ArgumentError: column name :review_date not found in the data frame

Eliminare in sicurezza una colonna assente

# Con Cols
select(chocolates, Not(Cols(==("review_date"))))

1795×9 DataFrame 
Row company  bean_origin REF   cocoa   company_location rating  bean_type bean_location
    String   String      Int64 Float64 String31         Float64 String31? String31?
...

# Con regex
select(chocolates, Not(r"review\_date"))

1795×9 DataFrame 
Row company  bean_origin REF   cocoa   company_location rating  bean_type bean_location
    String   String      Int64 Float64 String31         Float64 String31? String31?
...

Riordinare le colonne

# Cioccolate preselezionate
first(chocolates)

1795x5 DataFrame
Row  company   review_date  cocoa    rating   bean_location 
     String    Int64        Float64  Float64  String31?
__________________________________________________________
1    A. Morin  2016         63.0     3.75     Sao Tome

Spostala a sinistra

# Sposta cocoa a sinistra
select(chocolates, :cocoa, :)

1795x5 DataFrame
Row  cocoa    company   review_date  rating   bean_location 
     Float64  String    Int64        Float64  String31?
__________________________________________________________
1    63.0     A. Morin  2016         3.75     Sao Tome
...

Spostale a sinistra

# Sposta cocoa e rating a sinistra
select(chocolates, :cocoa, :rating, :)

1795x5 DataFrame

Row  cocoa    rating   company   review_date  bean_location 
     Float64  Float64  String    Int64        String31?
__________________________________________________________
1    63.0     3.75     A. Morin  2016         Sao Tome
...

Spostala a destra

# Sposta company a destra
select(chocolates, Not(:company), :company)

1795x5 DataFrame
Row  review_date  cocoa    rating   bean_location  company
     Int64        Float64  Float64  String31?      String
__________________________________________________________
1    2016         63.0     3.75     Sao Tome       A. Morin
...

Spostale in giro

# Combina i due spostamenti
select(chocolates, :cocoa, :rating, Not(:company), :company)

1795x5 DataFrame
Row cocoa    rating   bean_location  review_date  company 
    Float64  Float64  String31       Int64        String
__________________________________________________________
1   63.0     3.75     Sao Tome       2016         A. Morin
...

Sposta ed elimina insieme

# Riordina ed elimina review_date
# Combina i due spostamenti
select(chocolates, :cocoa, :rating, Not([:company, :review_date]), :company)

1795x4 DataFrame
Row cocoa    rating   bean_location  company 
    Float64  Float64  String31       String
__________________________________________________________
1   63.0     3.75     Sao Tome       A. Morin
...

Promemoria

Eliminare colonne:

# Elimina col1 e col 2
select(df, Not([:col1, "col 2"]))

Eliminare colonne in modo sicuro:

# Elimina col1 e col 2 che potrebbero non esistere
select(df, Not(r"col1"), Not(Cols(==("col 2"))))

Spostare colonne a sinistra

# Sposta col1 e col 2 a sinistra
select(df, :col1, "col 2", :)

Spostare colonne a destra

# Sposta col1 e col 2 a destra
select(df, Not([:col1, "col 2"]) ,:col1, "col 2")

Ayo berlatih!

Manipolazione dei dati in Julia