polars_core/
functions.rs

1//! # Functions
2//!
3//! Functions that might be useful.
4//!
5pub use crate::frame::horizontal::concat_df_horizontal;
6#[cfg(feature = "diagonal_concat")]
7use crate::prelude::*;
8#[cfg(feature = "diagonal_concat")]
9use crate::utils::concat_df;
10
11/// Concat [`DataFrame`]s diagonally.
12#[cfg(feature = "diagonal_concat")]
13/// Concat diagonally thereby combining different schemas.
14pub fn concat_df_diagonal(dfs: &[DataFrame]) -> PolarsResult<DataFrame> {
15    // TODO! replace with lazy only?
16    let upper_bound_width = dfs.iter().map(|df| df.width()).sum();
17    let mut column_names = PlHashSet::with_capacity(upper_bound_width);
18    let mut schema = Vec::with_capacity(upper_bound_width);
19
20    for df in dfs {
21        df.get_columns().iter().for_each(|s| {
22            let name = s.name().clone();
23            if column_names.insert(name.clone()) {
24                schema.push((name, s.dtype()))
25            }
26        });
27    }
28
29    let dfs = dfs
30        .iter()
31        .map(|df| {
32            let height = df.height();
33            let mut columns = Vec::with_capacity(schema.len());
34
35            for (name, dtype) in &schema {
36                match df.column(name.as_str()).ok() {
37                    Some(s) => columns.push(s.clone()),
38                    None => columns.push(Column::full_null(name.clone(), height, dtype)),
39                }
40            }
41            unsafe { DataFrame::new_no_checks(height, columns) }
42        })
43        .collect::<Vec<_>>();
44
45    concat_df(&dfs)
46}