Question

我有一个心率阵列。我想要的只是平均最后5分钟的心率。（数组包含超过最后一小时的心率）。

class HeartRate
{
    var hr = 0
    var date : Date?
}

var arrHeartRate = [HeartRate]()
let minDate = Date().addingTimeInterval(-300) //get 5min before time
var avgHR = self.arrHeartRate.filter { (Item) -> Bool in
                return Item.date! > minDate
            }.reduce(0) { (res, item) -> Result<Any, <#Error: Error#>> in
                return res
            }

Answer 1

以下是一些代码，它是不同stackoverflow答案的聚合。

class HeartRate
{
    var hr = 0
    var date: Date?
}

extension Collection where Iterator.Element == HeartRate, Index == Int {
    /// Returns the average of all elements in the array
    var average: Double {
        return isEmpty ? 0 : Double(reduce(0) { $0 + $1.hr }) / Double(endIndex-startIndex)
    }
}

var arrHeartRate = [HeartRate(), HeartRate()]
let minDate = Date().addingTimeInterval(-300) //get 5min before time
let rateInLast5Min = arrHeartRate.filter {
    guard let date = $0.date else { return false }
    return date > minDate
}
var avgHR = rateInLast5Min.average

Answer 2

您可以分两步进行过滤和缩小。首先，在时间范围内获得一组心率

<?php
        /**
        * Webkul Software.
        *
        * @category  Webkul
        * @package   Webkul_Marketplace
        * @author    Webkul
        * @copyright Copyright (c) 2010-2016 Webkul Software Private Limited (https://webkul.com)
        * @license   https://store.webkul.com/license.html
        */

        namespace Webkul\Marketplace\Controller\Account;

        use Magento\Framework\App\Action\Action;
        use Magento\Customer\Model\Session;
        use Magento\Framework\App\Action\Context;
        use Magento\Framework\Data\Form\FormKey\Validator as FormKeyValidator;
        use Magento\Framework\App\Filesystem\DirectoryList;
        use Magento\Framework\Filesystem;
        use Magento\Framework\App\RequestInterface;

        /**
        * Webkul Marketplace Account SaveAreaInfo Controller.
        */
        class Saveareainfo extends Action
        {

        public function __construct()
            {               
                parent::__construct();
            }

            public function execute()
            {

                die( " Hello Test ..   "  );


            }

        }

或者进行一些调整以从过滤后的数组中排除零日期

let filtered = arrHeartRate.filter{$0.date ?? Date() > minDate}

然后计算平均值并返回

let filtered = arrHeartRate.filter{$0.date ?? Date().addingTimeInterval(-500) > minDate}

Answer 3

我没有运行它，但有一些调整应该是你正在寻找的

    let rateInLast5Min = arrHeartRate.filter({ 0$.date! > minDate  })
let hours = rateInLast5Min.map{ return $0.hr }.reduce(0, +)
let average = Double(hours)/Double(rateInLast5Min.count)

Swift减少功能问题

3 个答案: