polars.arctan2#

polars.arctan2(y: str | Expr, x: str | Expr) → Expr[source]#

Compute two argument arctan in radians.

Returns the angle (in radians) in the plane between the positive x-axis and the ray from the origin to (x,y).

Parameters:

y: Column name or Expression.
x: Column name or Expression.

Examples

>>> import math
>>> twoRootTwo = math.sqrt(2) / 2
>>> df = pl.DataFrame(
...     {
...         "y": [twoRootTwo, -twoRootTwo, twoRootTwo, -twoRootTwo],
...         "x": [twoRootTwo, twoRootTwo, -twoRootTwo, -twoRootTwo],
...     }
... )
>>> df.select(
...     pl.arctan2d("y", "x").alias("atan2d"), pl.arctan2("y", "x").alias("atan2")
... )
shape: (4, 2)
┌────────┬───────────┐
│ atan2d ┆ atan2     │
│ ---    ┆ ---       │
│ f64    ┆ f64       │
╞════════╪═══════════╡
│ 45.0   ┆ 0.785398  │
│ -45.0  ┆ -0.785398 │
│ 135.0  ┆ 2.356194  │
│ -135.0 ┆ -2.356194 │
└────────┴───────────┘