import polars as pl
import scipy as sp
import numpy as np

df = pl.DataFrame({
    "species": ["A", "B", "C"],
    "N": [57, 72, 53]
})

df

shape: (3, 2)

species	N
str	i64
"A"	57
"B"	72
"C"	53

def tdf(N):
    return sp.stats.t(df = N - 1).ppf(0.975)

tdf(57)

np.float64(2.003240718847872)

(df
    .with_columns(pl.col("N").map_batches(tdf).alias("t"))
    .with_columns((pl.col("t") + 1).alias("other"))
)

shape: (3, 4)

species	N	t	other
str	i64	f64	f64
"A"	57	2.003241	3.003241
"B"	72	1.993943	2.993943
"C"	53	2.006647	3.006647

tdf(np.array([56, 57, 59]))

array([2.00404478, 2.00324072, 2.00171748])