---
title: "mapMissing(_:)"
framework: createml
role: symbol
role_heading: Instance Method
path: "createml/mluntypedcolumn/mapmissing(_:)"
---

# mapMissing(_:)

Creates a new column of typed values by applying the given thread-safe transform to every element of this untyped column, including missing elements.

## Declaration

```swift
func mapMissing<T>(_ lazyTransform: @escaping (MLDataValue) -> T?) -> MLDataColumn<T> where T : MLDataValueConvertible
```

## Parameters

- `lazyTransform`: A thread-safe element transformation function. The implementation of the transform you provide should accept an element of the column and return a transformed value of a type that conforms to doc://com.apple.createml/documentation/CreateML/MLDataValueConvertible. If the transform returns nil for a given element, the corresponding element in the new column will have a missing value.

## Return Value

Return Value A new MLDataColumn column.

## See Also

### Transforming elements to generate a data column

- [map(_:)](createml/mluntypedcolumn/map(_:).md)
- [map(_:)](createml/mluntypedcolumn/map(_:)-139qy.md)
- [map(_:)](createml/mluntypedcolumn/map(_:)-9v61j.md)