polars_core/chunked_array/ops/
fill_null.rs

1use arrow::bitmap::{Bitmap, BitmapBuilder};
2use arrow::legacy::kernels::set::set_at_nulls;
3use bytemuck::Zeroable;
4use num_traits::{NumCast, One, Zero};
5use polars_utils::itertools::Itertools;
6
7use crate::prelude::*;
8
9fn err_fill_null() -> PolarsError {
10    polars_err!(ComputeError: "could not determine the fill value")
11}
12
13impl Series {
14    /// Replace None values with one of the following strategies:
15    /// * Forward fill (replace None with the previous value)
16    /// * Backward fill (replace None with the next value)
17    /// * Mean fill (replace None with the mean of the whole array)
18    /// * Min fill (replace None with the minimum of the whole array)
19    /// * Max fill (replace None with the maximum of the whole array)
20    /// * Zero fill (replace None with the value zero)
21    /// * One fill (replace None with the value one)
22    ///
23    /// *NOTE: If you want to fill the Nones with a value use the
24    /// [`fill_null` operation on `ChunkedArray<T>`](crate::chunked_array::ops::ChunkFillNullValue)*.
25    ///
26    /// # Example
27    ///
28    /// ```rust
29    /// # use polars_core::prelude::*;
30    /// fn example() -> PolarsResult<()> {
31    ///     let s = Column::new("some_missing".into(), &[Some(1), None, Some(2)]);
32    ///
33    ///     let filled = s.fill_null(FillNullStrategy::Forward(None))?;
34    ///     assert_eq!(Vec::from(filled.i32()?), &[Some(1), Some(1), Some(2)]);
35    ///
36    ///     let filled = s.fill_null(FillNullStrategy::Backward(None))?;
37    ///     assert_eq!(Vec::from(filled.i32()?), &[Some(1), Some(2), Some(2)]);
38    ///
39    ///     let filled = s.fill_null(FillNullStrategy::Min)?;
40    ///     assert_eq!(Vec::from(filled.i32()?), &[Some(1), Some(1), Some(2)]);
41    ///
42    ///     let filled = s.fill_null(FillNullStrategy::Max)?;
43    ///     assert_eq!(Vec::from(filled.i32()?), &[Some(1), Some(2), Some(2)]);
44    ///
45    ///     let filled = s.fill_null(FillNullStrategy::Mean)?;
46    ///     assert_eq!(Vec::from(filled.i32()?), &[Some(1), Some(1), Some(2)]);
47    ///
48    ///     let filled = s.fill_null(FillNullStrategy::Zero)?;
49    ///     assert_eq!(Vec::from(filled.i32()?), &[Some(1), Some(0), Some(2)]);
50    ///
51    ///     let filled = s.fill_null(FillNullStrategy::One)?;
52    ///     assert_eq!(Vec::from(filled.i32()?), &[Some(1), Some(1), Some(2)]);
53    ///
54    ///     Ok(())
55    /// }
56    /// example();
57    /// ```
58    pub fn fill_null(&self, strategy: FillNullStrategy) -> PolarsResult<Series> {
59        // Nothing to fill.
60        let nc = self.null_count();
61        if nc == 0
62            || (nc == self.len()
63                && matches!(
64                    strategy,
65                    FillNullStrategy::Forward(_)
66                        | FillNullStrategy::Backward(_)
67                        | FillNullStrategy::Max
68                        | FillNullStrategy::Min
69                        | FillNullStrategy::Mean
70                ))
71        {
72            return Ok(self.clone());
73        }
74
75        let physical_type = self.dtype().to_physical();
76
77        match strategy {
78            FillNullStrategy::Forward(None) if !physical_type.is_primitive_numeric() => {
79                fill_forward_gather(self)
80            },
81
82            // Fast path to remove limit.
83            FillNullStrategy::Forward(Some(limit)) if limit >= nc as IdxSize => {
84                self.fill_null(FillNullStrategy::Forward(None))
85            },
86            FillNullStrategy::Backward(Some(limit)) if limit >= nc as IdxSize => {
87                self.fill_null(FillNullStrategy::Backward(None))
88            },
89
90            FillNullStrategy::Forward(Some(limit)) => fill_forward_gather_limit(self, limit),
91            FillNullStrategy::Backward(None) if !physical_type.is_primitive_numeric() => {
92                fill_backward_gather(self)
93            },
94            FillNullStrategy::Backward(Some(limit)) => fill_backward_gather_limit(self, limit),
95            #[cfg(feature = "dtype-decimal")]
96            FillNullStrategy::One if self.dtype().is_decimal() => {
97                use polars_compute::decimal::i128_to_dec128;
98
99                let ca = self.decimal().unwrap();
100                let precision = ca.precision();
101                let scale = ca.scale();
102                let fill_value = i128_to_dec128(1, precision, scale).ok_or_else(|| {
103                    polars_err!(ComputeError: "value '1' is out of range for Decimal({precision}, {scale})")
104                })?;
105                let phys = ca.physical().fill_null_with_values(fill_value)?;
106                Ok(phys.into_decimal_unchecked(precision, scale).into_series())
107            },
108            _ => {
109                let logical_type = self.dtype();
110                let s = self.to_physical_repr();
111                use DataType::*;
112                let out = match s.dtype() {
113                    Boolean => fill_null_bool(s.bool().unwrap(), strategy),
114                    String => {
115                        let s = unsafe { s.cast_unchecked(&Binary)? };
116                        let out = s.fill_null(strategy)?;
117                        return unsafe { out.cast_unchecked(&String) };
118                    },
119                    Binary => {
120                        let ca = s.binary().unwrap();
121                        fill_null_binary(ca, strategy).map(|ca| ca.into_series())
122                    },
123                    dt if dt.is_primitive_numeric() => {
124                        with_match_physical_numeric_polars_type!(dt, |$T| {
125                            let ca: &ChunkedArray<$T> = s.as_ref().as_ref().as_ref();
126                                fill_null_numeric(ca, strategy).map(|ca| ca.into_series())
127                        })
128                    },
129                    dt => {
130                        polars_bail!(InvalidOperation: "fill null strategy not yet supported for dtype: {}", dt)
131                    },
132                }?;
133                unsafe { out.from_physical_unchecked(logical_type) }
134            },
135        }
136    }
137}
138
139fn fill_forward_numeric<'a, T, I>(ca: &'a ChunkedArray<T>) -> ChunkedArray<T>
140where
141    T: PolarsDataType,
142    &'a ChunkedArray<T>: IntoIterator<IntoIter = I>,
143    I: TrustedLen + Iterator<Item = Option<T::Physical<'a>>>,
144    T::ZeroablePhysical<'a>: Copy,
145{
146    // Compute values.
147    let values: Vec<T::ZeroablePhysical<'a>> = ca
148        .into_iter()
149        .scan(T::ZeroablePhysical::zeroed(), |prev, v| {
150            *prev = v.map(|v| v.into()).unwrap_or(*prev);
151            Some(*prev)
152        })
153        .collect_trusted();
154
155    // Compute bitmask.
156    let num_start_nulls = ca.first_non_null().unwrap_or(ca.len());
157    let mut bm = BitmapBuilder::with_capacity(ca.len());
158    bm.extend_constant(num_start_nulls, false);
159    bm.extend_constant(ca.len() - num_start_nulls, true);
160    ChunkedArray::from_chunk_iter_like(
161        ca,
162        [
163            T::Array::from_zeroable_vec(values, ca.dtype().to_arrow(CompatLevel::newest()))
164                .with_validity_typed(bm.into_opt_validity()),
165        ],
166    )
167}
168
169fn fill_backward_numeric<'a, T, I>(ca: &'a ChunkedArray<T>) -> ChunkedArray<T>
170where
171    T: PolarsDataType,
172    &'a ChunkedArray<T>: IntoIterator<IntoIter = I>,
173    I: TrustedLen + Iterator<Item = Option<T::Physical<'a>>> + DoubleEndedIterator,
174    T::ZeroablePhysical<'a>: Copy,
175{
176    // Compute values.
177    let values: Vec<T::ZeroablePhysical<'a>> = ca
178        .into_iter()
179        .rev()
180        .scan(T::ZeroablePhysical::zeroed(), |prev, v| {
181            *prev = v.map(|v| v.into()).unwrap_or(*prev);
182            Some(*prev)
183        })
184        .collect_reversed();
185
186    // Compute bitmask.
187    let num_end_nulls = ca
188        .last_non_null()
189        .map(|i| ca.len() - 1 - i)
190        .unwrap_or(ca.len());
191    let mut bm = BitmapBuilder::with_capacity(ca.len());
192    bm.extend_constant(ca.len() - num_end_nulls, true);
193    bm.extend_constant(num_end_nulls, false);
194    ChunkedArray::from_chunk_iter_like(
195        ca,
196        [
197            T::Array::from_zeroable_vec(values, ca.dtype().to_arrow(CompatLevel::newest()))
198                .with_validity_typed(bm.into_opt_validity()),
199        ],
200    )
201}
202
203fn fill_null_numeric<T>(
204    ca: &ChunkedArray<T>,
205    strategy: FillNullStrategy,
206) -> PolarsResult<ChunkedArray<T>>
207where
208    T: PolarsNumericType,
209    ChunkedArray<T>: ChunkAgg<T::Native>,
210{
211    // Nothing to fill.
212    let mut out = match strategy {
213        FillNullStrategy::Min => {
214            ca.fill_null_with_values(ChunkAgg::min(ca).ok_or_else(err_fill_null)?)?
215        },
216        FillNullStrategy::Max => {
217            ca.fill_null_with_values(ChunkAgg::max(ca).ok_or_else(err_fill_null)?)?
218        },
219        FillNullStrategy::Mean => ca.fill_null_with_values(
220            ca.mean()
221                .map(|v| NumCast::from(v).unwrap())
222                .ok_or_else(err_fill_null)?,
223        )?,
224        FillNullStrategy::One => return ca.fill_null_with_values(One::one()),
225        FillNullStrategy::Zero => return ca.fill_null_with_values(Zero::zero()),
226        FillNullStrategy::Forward(None) => fill_forward_numeric(ca),
227        FillNullStrategy::Backward(None) => fill_backward_numeric(ca),
228        // Handled earlier
229        FillNullStrategy::Forward(_) => unreachable!(),
230        FillNullStrategy::Backward(_) => unreachable!(),
231    };
232    out.rename(ca.name().clone());
233    Ok(out)
234}
235
236fn fill_with_gather<F: Fn(&Bitmap) -> Vec<IdxSize>>(
237    s: &Series,
238    bits_to_idx: F,
239) -> PolarsResult<Series> {
240    let s = s.rechunk();
241    let arr = s.chunks()[0].clone();
242    let validity = arr.validity().expect("nulls");
243
244    let idx = bits_to_idx(validity);
245
246    Ok(unsafe { s.take_slice_unchecked(&idx) })
247}
248
249fn fill_forward_gather(s: &Series) -> PolarsResult<Series> {
250    fill_with_gather(s, |validity| {
251        let mut last_valid = 0;
252        validity
253            .iter()
254            .enumerate_idx()
255            .map(|(i, v)| {
256                if v {
257                    last_valid = i;
258                    i
259                } else {
260                    last_valid
261                }
262            })
263            .collect::<Vec<_>>()
264    })
265}
266
267fn fill_forward_gather_limit(s: &Series, limit: IdxSize) -> PolarsResult<Series> {
268    fill_with_gather(s, |validity| {
269        let mut last_valid = 0;
270        let mut conseq_invalid_count = 0;
271        validity
272            .iter()
273            .enumerate_idx()
274            .map(|(i, v)| {
275                if v {
276                    last_valid = i;
277                    conseq_invalid_count = 0;
278                    i
279                } else if conseq_invalid_count < limit {
280                    conseq_invalid_count += 1;
281                    last_valid
282                } else {
283                    i
284                }
285            })
286            .collect::<Vec<_>>()
287    })
288}
289
290fn fill_backward_gather(s: &Series) -> PolarsResult<Series> {
291    fill_with_gather(s, |validity| {
292        let last = validity.len() as IdxSize - 1;
293        let mut last_valid = last;
294        unsafe {
295            validity
296                .iter()
297                .rev()
298                .enumerate_idx()
299                .map(|(i, v)| {
300                    if v {
301                        last_valid = last - i;
302                        last - i
303                    } else {
304                        last_valid
305                    }
306                })
307                .trust_my_length((last + 1) as usize)
308                .collect_reversed::<Vec<_>>()
309        }
310    })
311}
312
313fn fill_backward_gather_limit(s: &Series, limit: IdxSize) -> PolarsResult<Series> {
314    fill_with_gather(s, |validity| {
315        let last = validity.len() as IdxSize - 1;
316        let mut last_valid = last;
317        let mut conseq_invalid_count = 0;
318        unsafe {
319            validity
320                .iter()
321                .rev()
322                .enumerate_idx()
323                .map(|(i, v)| {
324                    if v {
325                        last_valid = last - i;
326                        conseq_invalid_count = 0;
327                        last - i
328                    } else if conseq_invalid_count < limit {
329                        conseq_invalid_count += 1;
330                        last_valid
331                    } else {
332                        last - i
333                    }
334                })
335                .trust_my_length((last + 1) as usize)
336                .collect_reversed()
337        }
338    })
339}
340
341fn fill_null_bool(ca: &BooleanChunked, strategy: FillNullStrategy) -> PolarsResult<Series> {
342    match strategy {
343        FillNullStrategy::Min => ca
344            .fill_null_with_values(ca.min().ok_or_else(err_fill_null)?)
345            .map(|ca| ca.into_series()),
346        FillNullStrategy::Max => ca
347            .fill_null_with_values(ca.max().ok_or_else(err_fill_null)?)
348            .map(|ca| ca.into_series()),
349        FillNullStrategy::Mean => polars_bail!(opq = mean, "Boolean"),
350        FillNullStrategy::One => ca.fill_null_with_values(true).map(|ca| ca.into_series()),
351        FillNullStrategy::Zero => ca.fill_null_with_values(false).map(|ca| ca.into_series()),
352        FillNullStrategy::Forward(_) => unreachable!(),
353        FillNullStrategy::Backward(_) => unreachable!(),
354    }
355}
356
357fn fill_null_binary(ca: &BinaryChunked, strategy: FillNullStrategy) -> PolarsResult<BinaryChunked> {
358    match strategy {
359        FillNullStrategy::Min => {
360            ca.fill_null_with_values(ca.min_binary().ok_or_else(err_fill_null)?)
361        },
362        FillNullStrategy::Max => {
363            ca.fill_null_with_values(ca.max_binary().ok_or_else(err_fill_null)?)
364        },
365        FillNullStrategy::Zero => ca.fill_null_with_values(&[]),
366        FillNullStrategy::Forward(_) => unreachable!(),
367        FillNullStrategy::Backward(_) => unreachable!(),
368        strat => polars_bail!(InvalidOperation: "fill-null strategy {:?} is not supported", strat),
369    }
370}
371
372impl<T> ChunkFillNullValue<T::Native> for ChunkedArray<T>
373where
374    T: PolarsNumericType,
375{
376    fn fill_null_with_values(&self, value: T::Native) -> PolarsResult<Self> {
377        Ok(self.apply_kernel(&|arr| Box::new(set_at_nulls(arr, value))))
378    }
379}
380
381impl ChunkFillNullValue<bool> for BooleanChunked {
382    fn fill_null_with_values(&self, value: bool) -> PolarsResult<Self> {
383        self.set(&self.is_null(), Some(value))
384    }
385}
386
387impl ChunkFillNullValue<&[u8]> for BinaryChunked {
388    fn fill_null_with_values(&self, value: &[u8]) -> PolarsResult<Self> {
389        self.set(&self.is_null(), Some(value))
390    }
391}
polars_core/chunked_array/ops/fill_null.rs

polars_core/chunked_array/ops/
fill_null.rs
