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            FillNullStrategy::Forward(Some(limit)) => fill_forward_gather_limit(self, limit),
82            FillNullStrategy::Backward(None) if !physical_type.is_primitive_numeric() => {
83                fill_backward_gather(self)
84            },
85            FillNullStrategy::Backward(Some(limit)) => fill_backward_gather_limit(self, limit),
86            #[cfg(feature = "dtype-decimal")]
87            FillNullStrategy::One if self.dtype().is_decimal() => {
88                use polars_compute::decimal::i128_to_dec128;
89
90                let ca = self.decimal().unwrap();
91                let precision = ca.precision();
92                let scale = ca.scale();
93                let fill_value = i128_to_dec128(1, precision, scale).ok_or_else(|| {
94                    polars_err!(ComputeError: "value '1' is out of range for Decimal({precision}, {scale})")
95                })?;
96                let phys = ca.physical().fill_null_with_values(fill_value)?;
97                Ok(phys.into_decimal_unchecked(precision, scale).into_series())
98            },
99            _ => {
100                let logical_type = self.dtype();
101                let s = self.to_physical_repr();
102                use DataType::*;
103                let out = match s.dtype() {
104                    Boolean => fill_null_bool(s.bool().unwrap(), strategy),
105                    String => {
106                        let s = unsafe { s.cast_unchecked(&Binary)? };
107                        let out = s.fill_null(strategy)?;
108                        return unsafe { out.cast_unchecked(&String) };
109                    },
110                    Binary => {
111                        let ca = s.binary().unwrap();
112                        fill_null_binary(ca, strategy).map(|ca| ca.into_series())
113                    },
114                    dt if dt.is_primitive_numeric() => {
115                        with_match_physical_numeric_polars_type!(dt, |$T| {
116                            let ca: &ChunkedArray<$T> = s.as_ref().as_ref().as_ref();
117                                fill_null_numeric(ca, strategy).map(|ca| ca.into_series())
118                        })
119                    },
120                    dt => {
121                        polars_bail!(InvalidOperation: "fill null strategy not yet supported for dtype: {}", dt)
122                    },
123                }?;
124                unsafe { out.from_physical_unchecked(logical_type) }
125            },
126        }
127    }
128}
129
130fn fill_forward_numeric<'a, T, I>(ca: &'a ChunkedArray<T>) -> ChunkedArray<T>
131where
132    T: PolarsDataType,
133    &'a ChunkedArray<T>: IntoIterator<IntoIter = I>,
134    I: TrustedLen + Iterator<Item = Option<T::Physical<'a>>>,
135    T::ZeroablePhysical<'a>: Copy,
136{
137    // Compute values.
138    let values: Vec<T::ZeroablePhysical<'a>> = ca
139        .into_iter()
140        .scan(T::ZeroablePhysical::zeroed(), |prev, v| {
141            *prev = v.map(|v| v.into()).unwrap_or(*prev);
142            Some(*prev)
143        })
144        .collect_trusted();
145
146    // Compute bitmask.
147    let num_start_nulls = ca.first_non_null().unwrap_or(ca.len());
148    let mut bm = BitmapBuilder::with_capacity(ca.len());
149    bm.extend_constant(num_start_nulls, false);
150    bm.extend_constant(ca.len() - num_start_nulls, true);
151    ChunkedArray::from_chunk_iter_like(
152        ca,
153        [
154            T::Array::from_zeroable_vec(values, ca.dtype().to_arrow(CompatLevel::newest()))
155                .with_validity_typed(bm.into_opt_validity()),
156        ],
157    )
158}
159
160fn fill_backward_numeric<'a, T, I>(ca: &'a ChunkedArray<T>) -> ChunkedArray<T>
161where
162    T: PolarsDataType,
163    &'a ChunkedArray<T>: IntoIterator<IntoIter = I>,
164    I: TrustedLen + Iterator<Item = Option<T::Physical<'a>>> + DoubleEndedIterator,
165    T::ZeroablePhysical<'a>: Copy,
166{
167    // Compute values.
168    let values: Vec<T::ZeroablePhysical<'a>> = ca
169        .into_iter()
170        .rev()
171        .scan(T::ZeroablePhysical::zeroed(), |prev, v| {
172            *prev = v.map(|v| v.into()).unwrap_or(*prev);
173            Some(*prev)
174        })
175        .collect_reversed();
176
177    // Compute bitmask.
178    let num_end_nulls = ca
179        .last_non_null()
180        .map(|i| ca.len() - 1 - i)
181        .unwrap_or(ca.len());
182    let mut bm = BitmapBuilder::with_capacity(ca.len());
183    bm.extend_constant(ca.len() - num_end_nulls, true);
184    bm.extend_constant(num_end_nulls, false);
185    ChunkedArray::from_chunk_iter_like(
186        ca,
187        [
188            T::Array::from_zeroable_vec(values, ca.dtype().to_arrow(CompatLevel::newest()))
189                .with_validity_typed(bm.into_opt_validity()),
190        ],
191    )
192}
193
194fn fill_null_numeric<T>(
195    ca: &ChunkedArray<T>,
196    strategy: FillNullStrategy,
197) -> PolarsResult<ChunkedArray<T>>
198where
199    T: PolarsNumericType,
200    ChunkedArray<T>: ChunkAgg<T::Native>,
201{
202    // Nothing to fill.
203    let mut out = match strategy {
204        FillNullStrategy::Min => {
205            ca.fill_null_with_values(ChunkAgg::min(ca).ok_or_else(err_fill_null)?)?
206        },
207        FillNullStrategy::Max => {
208            ca.fill_null_with_values(ChunkAgg::max(ca).ok_or_else(err_fill_null)?)?
209        },
210        FillNullStrategy::Mean => ca.fill_null_with_values(
211            ca.mean()
212                .map(|v| NumCast::from(v).unwrap())
213                .ok_or_else(err_fill_null)?,
214        )?,
215        FillNullStrategy::One => return ca.fill_null_with_values(One::one()),
216        FillNullStrategy::Zero => return ca.fill_null_with_values(Zero::zero()),
217        FillNullStrategy::Forward(None) => fill_forward_numeric(ca),
218        FillNullStrategy::Backward(None) => fill_backward_numeric(ca),
219        // Handled earlier
220        FillNullStrategy::Forward(_) => unreachable!(),
221        FillNullStrategy::Backward(_) => unreachable!(),
222    };
223    out.rename(ca.name().clone());
224    Ok(out)
225}
226
227fn fill_with_gather<F: Fn(&Bitmap) -> Vec<IdxSize>>(
228    s: &Series,
229    bits_to_idx: F,
230) -> PolarsResult<Series> {
231    let s = s.rechunk();
232    let arr = s.chunks()[0].clone();
233    let validity = arr.validity().expect("nulls");
234
235    let idx = bits_to_idx(validity);
236
237    Ok(unsafe { s.take_slice_unchecked(&idx) })
238}
239
240fn fill_forward_gather(s: &Series) -> PolarsResult<Series> {
241    fill_with_gather(s, |validity| {
242        let mut last_valid = 0;
243        validity
244            .iter()
245            .enumerate_idx()
246            .map(|(i, v)| {
247                if v {
248                    last_valid = i;
249                    i
250                } else {
251                    last_valid
252                }
253            })
254            .collect::<Vec<_>>()
255    })
256}
257
258fn fill_forward_gather_limit(s: &Series, limit: IdxSize) -> PolarsResult<Series> {
259    fill_with_gather(s, |validity| {
260        let mut last_valid = 0;
261        let mut conseq_invalid_count = 0;
262        validity
263            .iter()
264            .enumerate_idx()
265            .map(|(i, v)| {
266                if v {
267                    last_valid = i;
268                    conseq_invalid_count = 0;
269                    i
270                } else if conseq_invalid_count < limit {
271                    conseq_invalid_count += 1;
272                    last_valid
273                } else {
274                    i
275                }
276            })
277            .collect::<Vec<_>>()
278    })
279}
280
281fn fill_backward_gather(s: &Series) -> PolarsResult<Series> {
282    fill_with_gather(s, |validity| {
283        let last = validity.len() as IdxSize - 1;
284        let mut last_valid = last;
285        unsafe {
286            validity
287                .iter()
288                .rev()
289                .enumerate_idx()
290                .map(|(i, v)| {
291                    if v {
292                        last_valid = last - i;
293                        last - i
294                    } else {
295                        last_valid
296                    }
297                })
298                .trust_my_length((last + 1) as usize)
299                .collect_reversed::<Vec<_>>()
300        }
301    })
302}
303
304fn fill_backward_gather_limit(s: &Series, limit: IdxSize) -> PolarsResult<Series> {
305    fill_with_gather(s, |validity| {
306        let last = validity.len() as IdxSize - 1;
307        let mut last_valid = last;
308        let mut conseq_invalid_count = 0;
309        unsafe {
310            validity
311                .iter()
312                .rev()
313                .enumerate_idx()
314                .map(|(i, v)| {
315                    if v {
316                        last_valid = last - i;
317                        conseq_invalid_count = 0;
318                        last - i
319                    } else if conseq_invalid_count < limit {
320                        conseq_invalid_count += 1;
321                        last_valid
322                    } else {
323                        last - i
324                    }
325                })
326                .trust_my_length((last + 1) as usize)
327                .collect_reversed()
328        }
329    })
330}
331
332fn fill_null_bool(ca: &BooleanChunked, strategy: FillNullStrategy) -> PolarsResult<Series> {
333    match strategy {
334        FillNullStrategy::Min => ca
335            .fill_null_with_values(ca.min().ok_or_else(err_fill_null)?)
336            .map(|ca| ca.into_series()),
337        FillNullStrategy::Max => ca
338            .fill_null_with_values(ca.max().ok_or_else(err_fill_null)?)
339            .map(|ca| ca.into_series()),
340        FillNullStrategy::Mean => polars_bail!(opq = mean, "Boolean"),
341        FillNullStrategy::One => ca.fill_null_with_values(true).map(|ca| ca.into_series()),
342        FillNullStrategy::Zero => ca.fill_null_with_values(false).map(|ca| ca.into_series()),
343        FillNullStrategy::Forward(_) => unreachable!(),
344        FillNullStrategy::Backward(_) => unreachable!(),
345    }
346}
347
348fn fill_null_binary(ca: &BinaryChunked, strategy: FillNullStrategy) -> PolarsResult<BinaryChunked> {
349    match strategy {
350        FillNullStrategy::Min => {
351            ca.fill_null_with_values(ca.min_binary().ok_or_else(err_fill_null)?)
352        },
353        FillNullStrategy::Max => {
354            ca.fill_null_with_values(ca.max_binary().ok_or_else(err_fill_null)?)
355        },
356        FillNullStrategy::Zero => ca.fill_null_with_values(&[]),
357        FillNullStrategy::Forward(_) => unreachable!(),
358        FillNullStrategy::Backward(_) => unreachable!(),
359        strat => polars_bail!(InvalidOperation: "fill-null strategy {:?} is not supported", strat),
360    }
361}
362
363impl<T> ChunkFillNullValue<T::Native> for ChunkedArray<T>
364where
365    T: PolarsNumericType,
366{
367    fn fill_null_with_values(&self, value: T::Native) -> PolarsResult<Self> {
368        Ok(self.apply_kernel(&|arr| Box::new(set_at_nulls(arr, value))))
369    }
370}
371
372impl ChunkFillNullValue<bool> for BooleanChunked {
373    fn fill_null_with_values(&self, value: bool) -> PolarsResult<Self> {
374        self.set(&self.is_null(), Some(value))
375    }
376}
377
378impl ChunkFillNullValue<&[u8]> for BinaryChunked {
379    fn fill_null_with_values(&self, value: &[u8]) -> PolarsResult<Self> {
380        self.set(&self.is_null(), Some(value))
381    }
382}
polars_core/chunked_array/ops/fill_null.rs

polars_core/chunked_array/ops/
fill_null.rs
