Sorting and summarizing a DataFrame
Introduction to Polars
Liam Brannigan
Data Scientist and Polars Contributor
Sorting
rentals.sort("price")
↓
shape: (5, 8)
| name | type | price | bedrooms | doubles | singles | review | beach |
| --- | --- | --- | --- | --- | --- | --- | --- |
| str | str | i64 | i64 | i64 | i64 | f64 | bool |
|----------------|---------|-------|----------|---------|---------|--------|-------|
| Porth Retreat | Cottage | 249 | 3 | 1 | 4 | null | true |
| Newquay Resort | Cottage | 315 | 3 | 1 | 4 | 7.30 | true |
| Perran View | Cottage | 341 | 3 | 1 | 4 | 8.20 | false |
| Porth Caravan | Caravan | 380 | 3 | 1 | 4 | 7.20 | true |
↑
Sorting in descending order
rentals.sort("price", descending=True)
shape: (5, 8)
| name | type | price | bedrooms | doubles | singles | review | beach |
| --- | --- | --- | --- | --- | --- | --- | --- |
| str | str | i64 | i64 | i64 | i64 | f64 | bool |
|----------------|---------|-------|----------|---------|---------|--------|-------|
| Tregenna House | Cottage | 2411 | 4 | 1 | 2 | 8.70 | true |
| Tregenna House | Cottage | 2182 | 4 | 1 | 2 | 8.70 | true |
| Tregenna House | Cottage | 1997 | 4 | 1 | 2 | 8.70 | true |
| Palma Villa | Cottage | 1947 | 4 | 1 | 2 | 9.60 | true |
| Palma Villa | Cottage | 1772 | 4 | 1 | 2 | 9.60 | true |
Sorting by multiple columns
rentals.sort("bedrooms","price")
↓
shape: (5, 8)
| name | type | price | bedrooms | doubles | singles | review | beach |
| --- | --- | --- | --- | --- | --- | --- | --- |
| str | str | i64 | i64 | i64 | i64 | f64 | bool |
|----------------|---------|-------|----------|---------|---------|--------|-------|
| Piran View | null | 775 | null | 1 | 3 | 9.60 | false |
| Porth Retreat | Cottage | 249 | 3 | 1 | 4 | null | true |
| Newquay Resort | Cottage | 315 | 3 | 1 | 4 | 7.30 | true |
| Perran View | Cottage | 341 | 3 | 1 | 4 | 8.20 | false |
| Porth Caravan | Caravan | 380 | 3 | 1 | 4 | 7.20 | true |
↑
Finding extreme values
rentals.top_k(3, by="price")
shape: (3, 8)
| name | type | price | bedrooms | doubles | singles | review | beach |
| --- | --- | --- | --- | --- | --- | --- | --- |
| str | str | i64 | i64 | i64 | i64 | f64 | bool |
|----------------|---------|-------|----------|---------|---------|--------|-------|
| Tregenna House | Cottage | 2411 | 4 | 1 | 2 | 8.70 | true |
| Tregenna House | Cottage | 2182 | 4 | 1 | 2 | 8.70 | true |
| Tregenna House | Cottage | 1997 | 4 | 1 | 2 | 8.70 | true |
Finding extreme values
rentals.bottom_k(3, by="price")
shape: (3, 8)
| name | type | price | bedrooms | doubles | singles | review | beach |
| --- | --- | --- | --- | --- | --- | --- | --- |
| str | str | i64 | i64 | i64 | i64 | f64 | bool |
|----------------|---------|-------|----------|---------|---------|--------|-------|
| Porth Retreat | Cottage | 249 | 3 | 1 | 4 | null | true |
| Newquay Resort | Cottage | 315 | 3 | 1 | 4 | 7.3 | true |
| Perran View | Hotel | 341 | 3 | 1 | 4 | 8.2 | false |
rentals.describe()
shape: (9, 9) | statistic | name | type | price | bedrooms | doubles | singles | review | beach | | --- | --- | --- | --- | --- | --- | --- | --- | --- | | str | str | str | f64 | f64 | f64 | f64 | f64 | f64 | |------------|------------------|-----------|---------|----------|---------|---------|--------|-------| | count | 49 | 48 | 49.00 | 48.00 | 49.00 | 45.00 | 47.00 | 49.00 | | null_count | 0 | 1 | 0.00 | 1.00 | 0.00 | 4.00 | 2.00 | 0.00 || mean | null | null | 973.10 | 3.69 | 1.43 | 3.22 | 8.99 | 0.63 | | std | null | null | 499.10 | 0.62 | 0.68 | 1.04 | 0.71 | null | | min | Atlantic Cottage | Apartment | 249.00 | 3.00 | 1.00 | 2.00 | 7.20 | 0.00 | | 25% | null | null | 600.00 | 3.00 | 1.00 | 2.00 | 8.70 | null | | 50% | null | null | 934.00 | 4.00 | 1.00 | 4.00 | 9.10 | null | | 75% | null | null | 1150.00 | 4.00 | 2.00 | 4.00 | 9.60 | null | | max | Wheal Frances | Cottage | 2411.00 | 5.00 | 3.00 | 6.00 | 9.90 | 1.00 |
Let's practice!
Introduction to Polars
