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# init(byConcatenatingMultiArrays:alongAxis:dataType:)

Merges an array of multiarrays into one multiarray along an axis.

```
convenience init(byConcatenatingMultiArrays multiArrays: [MLMultiArray], alongAxis axis: Int, dataType: MLMultiArrayDataType)
```

## Parameters

`multiArrays`

An [`MLMultiArray`](/documentation/CoreML/MLMultiArray) array.

`axis`

A zero-based axis number the instances in `multiArray` merge along.

`dataType`

An [`MLMultiArrayDataType`](/documentation/CoreML/MLMultiArrayDataType) instance that represents the underlying type of all the instances in `multiArrays`.

## Discussion

All multiarray instances in `multiArrays` must have:

- The same data type
- The same number of dimensions
- The same size for each corresponding dimension, except for the concatenation axis

For example, this code concatenates two multiarrays along their first dimension:

```swift
let multiarray1 = try MLMultiArray(shape: [1, 5, 7], dataType: .int32)
let multiarray2 = try MLMultiArray(shape: [2, 5, 7], dataType: .int32)

// Merge the two multiarrays along the first dimension.
let multiArray3 = MLMultiArray(concatenating: [multiarray1, multiarray2],
                               axis: 0,
                               dataType: .int32)

assert(multiArray3.shape == [3, 5, 7])
```

---

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