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| id: "duckdb-summarize" | |
| title: "Histogram" | |
| slug: "duckdb-histogram-query" | |
| description: "Create a histogram for a specific column to visualize the distribution of values." | |
| code: | | |
| from histogram( | |
| table_name, | |
| column_name, | |
| ) | |
| # DuckDB Histogram | |
| This snippet demonstrates how to use the `Histogram` function in DuckDB to calculate aggregate statistics for a dataset. The `histogram` function in DuckDB is used to compute histograms over columns of a dataset. It works for columns of any type and allows for various binning strategies and a custom number of bins. | |
| ```sql | |
| from histogram( | |
| table_name, | |
| column_name, | |
| bin_count := 10 | |
| ) | |
| ``` | |
| ## Parameters | |
| - `table_name`: The name of the table or a subquery result. | |
| - `column_name`: The name of the column for which to create the histogram, you can use different expressions to summarize the data such as length of a string. | |
| - `bin_count`: The number of bins to use in the histogram. (_**Optional**_) | |
| - `technique`: The binning technique to use. (_**Optional**_) | |
| ## Binning Techniques | |
| | Technique | Description | | |
| |-------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | |
| | `auto` | Automatically selects the best binning technique based on the data type. If the data type is not numeric or timestamp, it defaults to `sample`. For numeric or timestamp data, it defaults to `equi-width-nice`. | | |
| | `sample` | Uses distinct values in the column as bins. This technique is useful when the column has a small number of distinct values. | | |
| | `equi-height` | Creates bins such that each bin has approximately the same number of data points. This technique is useful for ensuring that each bin has a similar number of entries. This can be helpful for skewed distributions. | | |
| | `equi-width` | Creates bins of equal width. This technique is useful for numeric data. You want each bin to cover the same range of values. | | |
| | `equi-width-nice` | Creates bins of equal width with "nice" boundaries. This technique is similar to `equi-width`. It adjusts the bin boundaries to be more human-readable (e.g., rounding to the nearest whole number). | | |
| You can find more information in the [PR](https://github.com/duckdb/duckdb/pull/12590) that added this feature. | |
| ## Histogram of the length of the input persona from the `PersonaHub` dataset | |
| ```sql | |
| from histogram( | |
| instruction, | |
| len("input persona"), | |
| bin_count := 5 | |
| ) | |
| ``` | |
| <iframe | |
| src="https://huggingface.co/datasets/proj-persona/PersonaHub/embed/viewer/instruction/train?sql_console=true&sql=from+histogram%28%0A++instruction%2C%0A++len%28%22input+persona%22%29%2C%0A++bin_count+%3A%3D+5%0A%29" | |
| frameborder="0" | |
| width="100%" | |
| height="560px" | |
| ></iframe> |