Method: Polars::DataFrame#with_columns

Defined in:

lib/polars/data_frame.rb

#with_columns(*exprs, **named_exprs) ⇒ DataFrame

Add columns to this DataFrame.

Added columns will replace existing columns with the same name.

Examples:

Pass an expression to add it as a new column.

df = Polars::DataFrame.new(
  {
    "a" => [1, 2, 3, 4],
    "b" => [0.5, 4, 10, 13],
    "c" => [true, true, false, true]
  }
)
df.with_columns((Polars.col("a") ** 2).alias("a^2"))
# =>
# shape: (4, 4)
# ┌─────┬──────┬───────┬─────┐
# │ a   ┆ b    ┆ c     ┆ a^2 │
# │ --- ┆ ---  ┆ ---   ┆ --- │
# │ i64 ┆ f64  ┆ bool  ┆ i64 │
# ╞═════╪══════╪═══════╪═════╡
# │ 1   ┆ 0.5  ┆ true  ┆ 1   │
# │ 2   ┆ 4.0  ┆ true  ┆ 4   │
# │ 3   ┆ 10.0 ┆ false ┆ 9   │
# │ 4   ┆ 13.0 ┆ true  ┆ 16  │
# └─────┴──────┴───────┴─────┘

Added columns will replace existing columns with the same name.

df.with_columns(Polars.col("a").cast(Polars::Float64))
# =>
# shape: (4, 3)
# ┌─────┬──────┬───────┐
# │ a   ┆ b    ┆ c     │
# │ --- ┆ ---  ┆ ---   │
# │ f64 ┆ f64  ┆ bool  │
# ╞═════╪══════╪═══════╡
# │ 1.0 ┆ 0.5  ┆ true  │
# │ 2.0 ┆ 4.0  ┆ true  │
# │ 3.0 ┆ 10.0 ┆ false │
# │ 4.0 ┆ 13.0 ┆ true  │
# └─────┴──────┴───────┘

Multiple columns can be added by passing a list of expressions.

df.with_columns(
  [
    (Polars.col("a") ** 2).alias("a^2"),
    (Polars.col("b") / 2).alias("b/2"),
    (Polars.col("c").not_).alias("not c"),
  ]
)
# =>
# shape: (4, 6)
# ┌─────┬──────┬───────┬─────┬──────┬───────┐
# │ a   ┆ b    ┆ c     ┆ a^2 ┆ b/2  ┆ not c │
# │ --- ┆ ---  ┆ ---   ┆ --- ┆ ---  ┆ ---   │
# │ i64 ┆ f64  ┆ bool  ┆ i64 ┆ f64  ┆ bool  │
# ╞═════╪══════╪═══════╪═════╪══════╪═══════╡
# │ 1   ┆ 0.5  ┆ true  ┆ 1   ┆ 0.25 ┆ false │
# │ 2   ┆ 4.0  ┆ true  ┆ 4   ┆ 2.0  ┆ false │
# │ 3   ┆ 10.0 ┆ false ┆ 9   ┆ 5.0  ┆ true  │
# │ 4   ┆ 13.0 ┆ true  ┆ 16  ┆ 6.5  ┆ false │
# └─────┴──────┴───────┴─────┴──────┴───────┘

Multiple columns also can be added using positional arguments instead of a list.

df.with_columns(
  (Polars.col("a") ** 2).alias("a^2"),
  (Polars.col("b") / 2).alias("b/2"),
  (Polars.col("c").not_).alias("not c"),
)
# =>
# shape: (4, 6)
# ┌─────┬──────┬───────┬─────┬──────┬───────┐
# │ a   ┆ b    ┆ c     ┆ a^2 ┆ b/2  ┆ not c │
# │ --- ┆ ---  ┆ ---   ┆ --- ┆ ---  ┆ ---   │
# │ i64 ┆ f64  ┆ bool  ┆ i64 ┆ f64  ┆ bool  │
# ╞═════╪══════╪═══════╪═════╪══════╪═══════╡
# │ 1   ┆ 0.5  ┆ true  ┆ 1   ┆ 0.25 ┆ false │
# │ 2   ┆ 4.0  ┆ true  ┆ 4   ┆ 2.0  ┆ false │
# │ 3   ┆ 10.0 ┆ false ┆ 9   ┆ 5.0  ┆ true  │
# │ 4   ┆ 13.0 ┆ true  ┆ 16  ┆ 6.5  ┆ false │
# └─────┴──────┴───────┴─────┴──────┴───────┘

Use keyword arguments to easily name your expression inputs.

df.with_columns(
  ab: Polars.col("a") * Polars.col("b"),
  not_c: Polars.col("c").not_
)
# =>
# shape: (4, 5)
# ┌─────┬──────┬───────┬──────┬───────┐
# │ a   ┆ b    ┆ c     ┆ ab   ┆ not_c │
# │ --- ┆ ---  ┆ ---   ┆ ---  ┆ ---   │
# │ i64 ┆ f64  ┆ bool  ┆ f64  ┆ bool  │
# ╞═════╪══════╪═══════╪══════╪═══════╡
# │ 1   ┆ 0.5  ┆ true  ┆ 0.5  ┆ false │
# │ 2   ┆ 4.0  ┆ true  ┆ 8.0  ┆ false │
# │ 3   ┆ 10.0 ┆ false ┆ 30.0 ┆ true  │
# │ 4   ┆ 13.0 ┆ true  ┆ 52.0 ┆ false │
# └─────┴──────┴───────┴──────┴───────┘

Parameters:

• exprs (Array) —

  Column(s) to add, specified as positional arguments. Accepts expression input. Strings are parsed as column names, other non-expression inputs are parsed as literals.

• named_exprs (Hash) —

  Additional columns to add, specified as keyword arguments. The columns will be renamed to the keyword used.

Returns:

• (DataFrame)

# File 'lib/polars/data_frame.rb', line 4695

def with_columns(*exprs, **named_exprs)
  lazy.with_columns(*exprs, **named_exprs).collect(_eager: true)
end