feat: Add {Expr,Series}.cos
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liamholmes31
commented
Jan 6, 2026
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| @pytest.mark.skipif(PANDAS_VERSION < (2, 1, 0), reason="nullable types require pandas2+") | ||
| def test_cos_dtype_pandas_pyarrow() -> None: |
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wasn't actually certain if this test was necessary given the above one?
liamholmes31
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Jan 6, 2026
narwhals/expr.py
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| |values: double | | ||
| |cos: double | | ||
| |---- | | ||
| |values: [[0,1.5707963267948966,3.141592653589793]]| |
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open to suggestions on making this output a bit less off-putting!
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Maybe something like:
result = df.with_columns(cos=nw.col("values").cos()).select(nw.all().round(4))
FBruzzesi
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Jan 6, 2026
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FBruzzesi
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Thanks @liamholmes31 🙏🏼
Happy to merge once CI get green(er) 🥦 (I think some of the values were copied-pasted from sine)
narwhals/expr.py
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| |values: double | | ||
| |cos: double | | ||
| |---- | | ||
| |values: [[0,1.5707963267948966,3.141592653589793]]| |
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Maybe something like:
result = df.with_columns(cos=nw.col("values").cos()).select(nw.all().round(4))
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oops forgot to check the doctests, thanks fixed and tidied the rounding here! 81e0448 |
FBruzzesi
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Jan 6, 2026
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Description
Added cos methods for nw.Expr and nw.Series
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