# Summarize Islands

Given a dataset with a date column, summarizes the data in terms of `islands`, which are periods of time where data exists. This is often useful in determining if your data has `gaps` where data does not exist, or exists under certain conditions.

You must set a buffer such as 7 DAYS which will determine the grain of time for which one island stops and another begins.

The result is a summarized table.

## Parameters

| Name               | Type         | Description                                                                                                                                                                                                                         | Is Optional |
| ------------------ | ------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------- |
| group\_cols        | column\_list | The column(s) used to partition you data into groups. Islands will be searched within each group                                                                                                                                    | True        |
| conditions         | math\_list   | A list of conditions for which to apply to the data before searching for islands. For example, \["COL1 > 0","COL1 IS NOT NULL"]                                                                                                     | True        |
| date\_col          | column       | The column used to create search for islands. This must be a date or datetime column.                                                                                                                                               |             |
| buffer\_date\_part | date\_part   | A valid SQL datepart to slice the date\_col. For interval types, see [this Snowflake doc.](https://docs.snowflake.com/en/sql-reference/data-types-datetime.html#interval-constants)                                                 |             |
| buffer\_size       | int          | An integer of how many `date_parts` will be considered to be a part of the same island. Larger numbers will cause more overlaps and therefore less islands, and smaller numbers will cause less overlaps and therefore more islands |             |

## Example

```python
ds = rasgo.get.dataset(4721)

test = ds.apply(date_col='YEAR',
                group_cols=['BABYNAME','STATE','GENDER'],
                buffer_date_part='MONTH',
                buffer_size=24,
                conditions=['BABYCOUNT>50']
                )

test.preview()

```

## Source Code

{% embed url="<https://github.com/rasgointelligence/RasgoTransforms/blob/main/rasgotransforms/rasgotransforms/transforms/summarize_islands/snowflake/summarize_islands.sql>" %}