Convert [MLMultiArray] to Float? - arrays

I have an MLMultiArray which is a result of an ML Model.
I need to convert it to Float so that I can further store it in Realm.
Below is an example of one of the MLMultiArray. The result from the ML Model contains 120 of the same vectors so its an array of MLMultiArrays i.e Array of Float32 1 x 128 matrices.
Float32 1 x 128 matrix
[4.476562,1.179688,0.07141113,6.976562,-0.2858887,-7.378906,0.6445312,3.695312,1.399414,2.486328,-3.988281,-0.2636719,1.000977,-4.480469,-7.832031,1.59082,0.8515625,-1.296875,-1.435547,7.839844,5.851562,0.3701172,-2.492188,7.273438,2.404297,-3.3125,-5.699219,-0.6816406,0.2807617,-3.882812,-3.982422,5.339844,4.125,-3.871094,0.6225586,1.712891,-10.02344,0.7119141,4.472656,3.566406,-0.559082,-1.049805,-4.679688,10.07812,-1.459961,4.707031,-6.078125,1.675781,-0.6259766,2.519531,3.472656,-3.400391,-6.714844,-4.933594,-1.733398,1.095703,-6.15625,9.234375,3.693359,-9.492188,0.8637695,0.8203125,-2.814453,-4.4375,-1.092773,3.332031,0.1623535,3.583984,-11.25781,-0.9941406,-0.3491211,1.464844,-1.579102,4.558594,2.703125,4.601562,5.914062,-2.402344,-5.46875,-0.355957,11.39062,2.070312,-7.289062,-0.4470215,-0.1595459,9.148438,1.833008,-2.097656,-3.9375,6.699219,-4.347656,-6.835938,-1.179688,3.910156,-13.07812,-1.947266,-0.9238281,-0.949707,-4.398438,2.363281,4.421875,4.632812,2.607422,8.773438,0.9106445,9.21875,-14.0625,-1.301758,-4.875,0.6054688,6.496094,-2.021484,3.898438,-4.644531,0.9853516,7.253906,3.066406,-1.051758,-8.09375,-6.527344,3.890625,5.175781,0.3701172,-0.5683594,-1.341797,0.1497803,4.074219,0.5932617]
Is there any way I can convert an array of MLMultiArray to Float32?
Any help would be appreciated <3


You can first convert the MLMultiArray to an UnsafeBufferPointer and then to a regular Array.
import CoreML
var a: [Float] = [ 1, 2, 3 ]
var m = try! MLMultiArray(a)
if let b = try? UnsafeBufferPointer<Float>(m) {
let c = Array(b)
print(c)
}


This is old question but this can help someone:
To convert from an MLMultiArray To An Array of primitive, You can use this function you will need just to change the output type
func convertToArray(from mlMultiArray: MLMultiArray) -> [Double] {
// Init our output array
var array: [Double] = []
// Get length
let length = mlMultiArray.count
// Set content of multi array to our out put array
for i in 0...length - 1 {
array.append(Double(truncating: mlMultiArray[[0,NSNumber(value: i)]]))
}
return array
}
To convert from an Array to MLMultiArray Use this, you may need to change the shape accordingly
func convertToMLMultiArray(from array: [Double]) -> MLMultiArray {
let length = NSNumber(value: array.count)
// Define shape of array
guard let mlMultiArray = try? MLMultiArray(shape:[1, length], dataType:MLMultiArrayDataType.double) else {
fatalError("Unexpected runtime error. MLMultiArray")
}
// Insert elements
for (index, element) in array.enumerated() {
mlMultiArray[index] = NSNumber(floatLiteral: element)
}
return mlMultiArray
}


I'm using this way, and subscript to access the element and it works fine for me.
const float *array = (float*)matrix.dataPointer

Related

Convert a 2d array of strings to a 2d array of double swift

I have 2 arrays:
var locationString = [[String]]()
var doubleArray = [[Double]]()
The array data is appended after a parser has ran just in case you are wondering why there is no data.
Essentially I am trying to convert the locationString from string to double.
I originally tried the following:
let doubleArray = locationString.map{ Double($0) }
but this does not seem to work as i get an error of:
Cannot invoke initializer for type 'Double' with an argument list of type ((String]))
Any help would be appreciated, thanks.

Use map with compactMap map:
let doubleArray = locationString.map { $0.compactMap(Double.init) }
Example:
let locationString = [["1.2", "2.3"], ["3.4", "4.4", "hello"]]
let doubleArray = locationString.map { $0.compactMap(Double.init) }
print(doubleArray) // [[1.2, 2.3], [3.4, 4.4]]
The outer map processes each array of strings. The inner compactMap converts the Strings to Double and drops them if the conversion returns nil because the String is not a valid Double.
To trim leading and trailing whitespace in your Strings before converting to Double, use .trimmingCharacters(in: .whitespaces):
let doubleArray = locationString.map { $0.compactMap { Double($0.trimmingCharacters(in: .whitespaces )) } }

N-Dimensional array swift

Is there any way to have an n dimensional array in swift? I would like to be able to make a function that creates an array with n dimensions but I cannot figure out how.
Basically something like this:
func ndarray <T> (dimensions: Int...) -> [[T]] { // What do I tell it I return?
var out
for d in dimensions {
out = Array<T>(repeating: out, count: d)
}
return out
}
The above code does not work for obvios reasons but, I think it points out the main problems I am having:
How do I define a return type
How do I actually create the array
Once created how do I traverse and populate the array

Here is the implementation of an N-Dimensional Array. It uses a normal array internally for storage and converts the multi-dimensional indices into a single index for the internal array.
struct NDimArray<T> {
let dimensions: [Int]
var data: [T]
init(dimensions: Int..., initialValue: T) {
self.dimensions = dimensions
data = Array(repeating: initialValue, count: dimensions.reduce(1, *))
}
init(dimensions: Int..., initUsing initializer: () -> T) {
self.dimensions = dimensions
data = (0 ..< dimensions.reduce(1, *)).map { _ in initializer() }
}
// Compute index into data from indices
private func computeIndex(_ indices: [Int]) -> Int {
guard indices.count == dimensions.count else { fatalError("Wrong number of indices: got \(indices.count), expected \(dimensions.count)") }
zip(dimensions, indices).forEach { dim, idx in
guard (0 ..< dim) ~= idx else { fatalError("Index out of range") }
}
var idx = indices
var dims = dimensions
var product = 1
var total = idx.removeLast()
while !idx.isEmpty {
product *= dims.removeLast()
total += (idx.removeLast() * product)
}
return total
}
subscript(_ indices: Int...) -> T {
get {
return data[computeIndex(indices)]
}
set {
data[computeIndex(indices)] = newValue
}
}
}
Example:
// Create a 3 x 4 x 5 array of String with initial value ""
var arr = NDimArray<String>(dimensions: 3, 4, 5, initialValue: "")
for x in 0 ..< 3 {
for y in 0 ..< 4 {
for z in 0 ..< 5 {
// Encode indices in the string
arr[x, y, z] = "(\(x),\(y),\(z))"
}
}
}
// Show internal storage of data
print(arr.data)
["(0,0,0)", "(0,0,1)", "(0,0,2)", "(0,0,3)", "(0,0,4)", "(0,1,0)", "(0,1,1)", "(0,1,2)", "(0,1,3)", "(0,1,4)", "(0,2,0)", "(0,2,1)", "(0,2,2)", "(0,2,3)", "(0,2,4)", "(0,3,0)", "(0,3,1)", "(0,3,2)", "(0,3,3)", "(0,3,4)", "(1,0,0)", "(1,0,1)", "(1,0,2)", "(1,0,3)", "(1,0,4)", "(1,1,0)", "(1,1,1)", "(1,1,2)", "(1,1,3)", "(1,1,4)", "(1,2,0)", "(1,2,1)", "(1,2,2)", "(1,2,3)", "(1,2,4)", "(1,3,0)", "(1,3,1)", "(1,3,2)", "(1,3,3)", "(1,3,4)", "(2,0,0)", "(2,0,1)", "(2,0,2)", "(2,0,3)", "(2,0,4)", "(2,1,0)", "(2,1,1)", "(2,1,2)", "(2,1,3)", "(2,1,4)", "(2,2,0)", "(2,2,1)", "(2,2,2)", "(2,2,3)", "(2,2,4)", "(2,3,0)", "(2,3,1)", "(2,3,2)", "(2,3,3)", "(2,3,4)"]
print(arr[2, 2, 2]) // "(2,2,2)"
print(arr[3, 0, 0]) // Fatal error: Index out of range
print(arr[0, 4, 0]) // Fatal error: Index out of range
print(arr[2]) // Fatal error: Wrong number of indices: got 1, expected 3
Initializing an Array with a Reference Type
As #DuncanC noted in the comments, you have to be careful when initializing an array with a value which is a reference type, because the array will be filled with references to the object and modifying the object at any index will modify all of them.
To solve this, I added a second initializer:
init(dimensions: Int..., initUsing initializer: () -> T)
which takes a closure () -> T which can be used to create a new object for each element of the array.
For example:
class Person {
var name = ""
}
// Pass a closure which creates a `Person` instance to fill the array
// with 25 person objects
let arr = NDimArray(dimensions: 5, 5, initUsing: { Person() })
arr[3, 3].name = "Fred"
arr[2, 2].name = "Wilma"
print(arr[3, 3].name, arr[2, 2].name)
Fred Wilma

Nope, it's not possible. Array dimensions is something that needs to be determined at compile time, while the argument you want to pass to the initializer will not be known until runtime. If you really want to achieve something like this, then you'll need to move the array indexing from compile time to runtime, e.g. by accessing the array via an array of indexes. Still you don't have compile validation, since the array length can at runtime to not match the dimensions of the array.
This problem is similar to the one that attempts to convert a tuple to an array.

String into array in Swift 3

I am trying to transform a string of the following format into an array (...of arrays, of floats!) in Swift 3:
"[173.0, 180.5],[173.0, 180.0],[174.0, 180.5],[174.0, 183.0]"
so that the output would be an array in this format:
[[173.0, 180.5, 173.0, 180.0],[174.0, 180.5, 174.0, 183.0]]
I am really new to Swift and struggling to find any String functions that will allow me to convert the data in this way. Any pointers on how I can do it would be awesome - thanks!

As Martin said, you first want to first convert this from a string to an array. In Swift 3:
let string = "[173.0, 180.5],[173.0, 180.0],[174.0, 180.5],[174.0, 183.0]"
let jsonString = "[" + string + "]"
guard let data = jsonString.data(using: .utf8),
let json = try? JSONSerialization.jsonObject(with: data),
let numberPairs = json as? [[Double]] else {
fatalError("string was not well-formed: \(string)")
}
You then want to combine these pairs of numbers together:
var combinedNumbers = [[Double]]()
var current: [Double]?
for numberPair in numberPairs {
if current != nil {
combinedNumbers.append(current! + numberPair)
current = nil
} else {
current = numberPair
}
}
// use `combinedNumbers` here
Clearly, you should use better variable names (perhaps something that suggests what these sets of numbers are), but hopefully this illustrates the idea.

Swift 4
You can use Decodable:
let str = "[173.0, 180.5],[173.0, 180.0],[174.0, 180.5],[174.0, 183.0]"
let json = "[\(str)]".data(using: .utf8)!
let numbers = try JSONDecoder().decode([[Double]].self, from: json).flatMap { $0 }
let result = stride(from: 0, to: numbers.count, by: 4).map { startIndex -> [Double] in
let endIndex = min(startIndex + 4, numbers.count)
return Array(numbers[startIndex..<endIndex])
}
Swift 3
One option is to use the old-school NSScanner to extract the numbers from the string to a flat array, then build a 2 dimensional array off that:
let str = "[173.0, 180.5],[173.0, 180.0],[174.0, 180.5],[174.0, 183.0]"
let scanner = Scanner(string: str)
scanner.charactersToBeSkipped = CharacterSet(charactersIn: "[], ")
// Build the flat array
var numbers = [Double]()
while !scanner.isAtEnd {
var d = 0.0
if scanner.scanDouble(&d) {
numbers.append(d)
}
}
// Now the 2 dimensional array
let result = stride(from: 0, to: numbers.count, by: 4).map { startIndex -> [Double] in
let endIndex = min(startIndex + 4, numbers.count)
return Array(numbers[startIndex..<endIndex])
}

One option to convert the data types would be to develop a simple algorithm that will iterate through the string and analyze elements and square bracket delimiters, returning the appropriate conversion.
Below is the skeleton of what the fundamental components of such a function could look like.
Included are some basic aspects of the conversion from string to array.
var str = "[173.0, 180.5], [173.0, 180.0],[174.0, 180.5],[174.0, 183.0]"
// Cast returns array ["[","1","7","3",".","0",",".......]
let array = Array(str.characters)
// Iterate through array
for char in array {
if char == "[" || char == "]" {
// Deal with array delimiters appropriately
}
...
}
It might help to check out this similar problem.
NOTE: As Martin R mentioned, JSON interpretation may be a good method as well.

How do I cast my array of arrays as a [[Double]] in Swift 3.0?

In Swift 2.3 I am able to take a [String:AnyObject] and cast it as! [[Double]]. However, using the same object in Swift 3.0, I am unable to cast it as a [[Double]]. When I cast it instead as a [[AnyObject]] or [[Any]], loop through and try and convert, I get the following error:
Could not cast value of type '__NSArrayI' (0x10783ec08) to 'NSNumber' (0x106e47320).
The following code works in my Swift 2.3 implementation, but NOT Swift 3.0
func extractCoordinatesForArea() {
// This first line is where it crashes
let theArraysOfCoordinates = myObject.geoArea!["geometry"]!["coordinates"] as! [[Double]]
var newArea:[CLLocationCoordinate2D] = []
for coordArray in theArraysOfCoordinates {
// x is LONG, LAT
let x = [coordArray[0], coordArray[1]]
// Reverse the coordinates because they are stored as LONG, LAT on the server
let y = CLLocationCoordinate2DMake(x[1],x[0])
print(y)
newArea.append(y)
}
}
While the error makes sense, I cannot seem to get this to work after having explicitly declared the type or converting in the for loop. Any help is greatly appreciated.

Try to break the first statement like this.
if let geometryDic = myObject.geoArea["geometry"] as? [String:Any],
let coordinatesArray = geometryDic["coordinates"] as? [Any] {
let theArraysOfCoordinates = coordinatesArray.first as? [[Double]] {
var newArea:[CLLocationCoordinate2D] = []
for coordArray in theArraysOfCoordinates {
//There is no need to create another array X you can directly use coordArray
// Reverse the coordinates because they are stored as LONG, LAT on the server
let coordinate = CLLocationCoordinate2DMake(coordArray[1],coordArray[0])
print(coordinate)
newArea.append(coordinate)
}
}

Converting Array Of String to Double and then calculating the sum in Swift

I have an array of Strings that i would like to convert to Double. Then i would like to add each item in the array together and get the sum.
this is my code so far, After enumerating the array I'm having issues adding all of them together.

update: Xcode 10.1 • Swift 4.2.1 or later
let strings = ["1.9","2.7","3.1","4.5","5.0"]
let doubles = strings.compactMap(Double.init)
let sum = doubles.reduce(0, +)
print(sum) // 17.2
If you dont need the intermediary collection
let sum = strings.reduce(0) { $0 + (Double($1) ?? .zero) }

Just map (iterate and convert each value in array) all values in array to Double and then reduce all Double values with start value 0 and closure (in your case it's just an operator) +.
reduce a collection of elements down to a single value by recursively applying the provided closure.
let stringDoubles = ["2.9","3.1","1.7","9.5","5.6"]
let sum = stringDoubles.map { Double($0)! }.reduce(0, combine: +)
print(sum) // "22.8". If start value was, for example, 10, print(sum) => "32.8"

Loop through the array,
for each string, convert the string to double using:
Double(string:String)
Then add each to the tally
var strings:[String] = ["1.3", "1", "8", "5", "bad number"]
var tally = 0.0
for eachString in strings{
// Convert each string to Double
if let num = Double(eachString) { //Double(String) returns an optional.
tally += num
} else {
print("Error converting to Double")
}
// Another way to convert if you don't need error handling
// NSString.doubleValue will just return 0.0 on a bad string.
// let num=(eachString as NSString).doubleValue
// tally += num
}
print(tally)

Here is an answer to your first part of your question in Swift 2.0:
I have an array of Strings that i would like to convert to Double. Then i would like to add each item in the array together and get the sum.
let myStrings = ["2", "3","5.6", "4", "6"]
let doubles = myStrings.map { (s : String) -> Double in
if let d = Double(s){
return d
}
return 0.0
}
let sum = doubles.reduce(0.0, combine: {(sum: Double, item:Double) ->Double in
return sum + item
})

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