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# prototype

A prototype that creates type-erased columns with the same underlying type as the column slice.

```
var prototype: any AnyColumnPrototype { get }
```

## Discussion

Use a type-erased column prototype to create new columns of the same type as the slice’s parent column
without explicitly knowing what type it is, by calling
the `prototype` property’s [`makeColumn(capacity:)`](/documentation/TabularData/AnyColumnPrototype/makeColumn(capacity:)) method.

```swift
// Get a type-erased column.
let someColumn: AnyColumn = dataFrame["someFeature"]

// Create a new column with the same type.
let newColumn = someColumn.prototype.makeColumn(capacity: 10)
```

---

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