---
title: "bandPart(lowerBandCount:upperBandCount:)"
framework: coreml
role: symbol
role_heading: Instance Method
path: "coreml/mltensor/bandpart(lowerbandcount:upperbandcount:)"
---

# bandPart(lowerBandCount:upperBandCount:)

Returns a new tensor with the same shape where everything outside a central band in each innermost matrix is set to zero.

## Declaration

```swift
func bandPart(lowerBandCount: Int, upperBandCount: Int) -> MLTensor
```

## Parameters

- `lowerBandCount`: The number of diagonals in the lower triangle to keep. If -1, keep the entire lower triangle.
- `upperBandCount`: The number of diagonals in the upper triangle to keep. If -1, keep the entire upper triangle.

## Return Value

Return Value The band part of the tensor.

## Discussion

Discussion The framework copies a diagonal band of values from the tensor to the result tensor of the same size. A coordinate [..., i, j] is considered in band if (lowerBandCount < 0 || (i-j) <= lowerBandCount) && (upperBandCount < 0 || (j-i) <= upperBandCount) Values outside of the band are set to 0. For example: let t = Tensor([     [ 5,  1,  2, 3],     [-1,  5,  1, 2],     [-2, -1,  5, 1],     [-3, -2, -1, 5] ], scalarType: Float.self)

t.bandPart(lowerBandCount: 0, upperBandCount: 0) // [[ 5,  0,  0, 0] //  [ 0,  5,  0, 0] //  [ 0,  0,  5, 0] //  [ 0,  0,  0, 5]]

t.bandPart(lowerBandCount: 0, upperBandCount: -1) // [[ 5,  1,  2, 3] //  [ 0,  5,  1, 2] //  [ 0,  0,  5, 1] //  [ 0,  0,  0, 5]]

t.bandPart(lowerBandCount: -1, upperBandCount: 0) // [[ 5,  0,  0, 0] //  [-1,  5,  0, 0] //  [-2, -1,  5, 0] //  [-3, -2, -1, 5]]

## See Also

### Accessing the extended tensor, sign and reciprocal

- [expandingShape(at:)](coreml/mltensor/expandingshape(at:).md)
- [tiled(multiples:)](coreml/mltensor/tiled(multiples:).md)
- [sign()](coreml/mltensor/sign().md)
- [reciprocal()](coreml/mltensor/reciprocal().md)