Kalman.swift

//TxPower given by Jérôme
let power = 62.0
// Truncate incoming RSSI
let incomingRSSI = Double(truncating: RSSI)

// Check if filter is already present for current peripheral
guard let filter = items[peripheral.identifier.uuidString] else {
    // Init the KalmanFilter
    items[peripheral.identifier.uuidString] = KalmanFilter(first: incomingRSSI)
    return
}
// Apply filter with new RSSI
filter.applyFilter(for: incomingRSSI)

/*
 * Compute distance using the following formula:
 *  10 ^ ((Measured Power – RSSI)/(10 * N))
 */
let distance = pow(10, ((power - filter.estimatedRSSI) / 40))

print("Found \"\(peripheral.identifier.uuidString)\" - RSSI: \(RSSI) - Distance is \(distance)")