Numpy's argmax() in Swift - swift

Question

I'm working on a project which converts user's face to emoji. I use Apple's ARKit in this purpose.
I need to get the most probable option. I wrote this code:
func renderer(for anchor: ARAnchor) {
guard let faceAnchor = anchor as? ARFaceAnchor else {
return
}
let shapes = faceAnchor.blendShapes
let browDownLeft = shapes[.browDownLeft]!.doubleValue
let browInnerUp = shapes[.browInnerUp]!.doubleValue
let browOuterUpLeft = shapes[.browOuterUpLeft]!.doubleValue
let leftBrowMax = max(browDownLeft, browInnerUp, browOuterUpLeft)
switch leftBrowMax {
case browDownLeft:
userFace.leftBrow = .browDown
case browInnerUp:
userFace.leftBrow = .browInnerUp
case browOuterUpLeft:
userFace.leftBrow = .browOuterUp
default:
userFace.leftBrow = .any
}
}
I need to duplicate function's body six time (for brows, eyes and mouth sides), so I want to write it in a more convenient way. Is there any options in Swift like numpy's argmax function? Also I need to specify arguments range, because arguments for mouth should not be compared with arguments for brows.

Answer 1

You can use something like this:
func maxBlendShape(for blendShapes: [ARFaceAnchor.BlendShapeLocation], in shape: [ARFaceAnchor.BlendShapeLocation: NSNumber]) -> Double? {
blendShapes
.compactMap { shape[$0] }
.map(\.doubleValue)
.max()
}
Usage would then be something like this:
maxBlendShape(for: [.browDownLeft, .browInnerUp, .browOuterUpLeft], in: faceAnchor.blendShapes)
Note: Nothing here is specific to ARKit, you just filter some keys from the dictionary and find their max value. A generic solution could look like this:
extension Dictionary where Value == NSNumber {
func maxDouble(for keys: [Key]) -> Double? {
keys
.compactMap({self[$0]})
.map(\.doubleValue)
.max()
}
}
faceAnchor.blendShapes.maxDouble(for: [.browInnerUp, .browDownLeft, .browOuterUpLeft])