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Clone a DataFrame

Source code

Description

This makes a very cheap deep copy/clone of an existing DataFrame. Rarely useful as DataFrames are nearly 100% immutable. Any modification of a DataFrame should lead to a clone anyways, but this can be useful when dealing with attributes (see examples).

Usage

<DataFrame>$clone()

Value

A DataFrame

Examples

library("polars")

df1 = as_polars_df(iris)

# Make a function to take a DataFrame, add an attribute, and return a DataFrame
give_attr = function(data) {
  attr(data, "created_on") = "2024-01-29"
  data
}
df2 = give_attr(df1)

# Problem: the original DataFrame also gets the attribute while it shouldn't!
attributes(df1)

#> $class
#> [1] "RPolarsDataFrame"
#> 
#> $created_on
#> [1] "2024-01-29"

# Use $clone() inside the function to avoid that
give_attr = function(data) {
  data = data$clone()
  attr(data, "created_on") = "2024-01-29"
  data
}
df1 = as_polars_df(iris)
df2 = give_attr(df1)

# now, the original DataFrame doesn't get this attribute
attributes(df1)

#> $class
#> [1] "RPolarsDataFrame"