Question

我使用以下php代码将温度传感器数据从MySQL数据库中提取到php文件中：

<?php
$hostname = 'xxxxx';
$username = 'xxxxx';
$password = 'xxxxx';
$dbname="measurements";
$usertable="temperature";

try {
$dbh = new PDO("mysql:host=$hostname;dbname=measurements", 
                           $username, $password);
/*** The SQL SELECT statement ***/
$sth = $dbh->prepare("
   SELECT
   ROUND(AVG(`temperature`),1) AS temperature,
   TIMESTAMP(LEFT(`dtg`,16)) AS dtg
   FROM `temperature`
   GROUP BY LEFT(`dtg`,16)
   ORDER BY `dtg` DESC
   LIMIT 0,800
");
$sth->execute();

/* Fetch all of the remaining rows in the result set */
$result = $sth->fetchAll(PDO::FETCH_ASSOC);
/*** close the database connection ***/
$dbh = null;

}
catch(PDOException $e)
{
    echo $e->getMessage();
}

function make_pair($date, $amount) {
return array($date, $amount);
}
$json_data = json_encode($result, JSON_NUMERIC_CHECK); 
?>

然后我使用javascript在flot图中绘制这些数据：

 <script type="text/javascript">
//put array into javascript variable

var dataset1 = <?php echo json_encode($result); ?>;

//plot
$(document).ready(function () {
    $.plot($("#placeholder"),  dataset1  );
});

</script>

当我在浏览器中打开php文件并查看javscript控制台时，我可以看到数据正好通过并保存为变量dataset1

看起来像这样：

//put array into javascript variable

var dataset1 = [{"temperature":"19.6","dtg":"2016-07-28 12:53:00"},{"temperature":"19.5","dtg":"2016-07-28 12:52:00"},{"temperature":"19.5","dtg":"2016-07-28 12:51:00"},{"temperature":"19.6","dtg":"2016-07-28 12:50:00"},{"temperature":"19.6","dtg":"2016-07-28 12:49:00"},{"temperature":"19.6","dtg":"2016-07-28 12:48:00"},{"temperature":"19.6","dtg":"2016-07-28 12:47:00"},{"temperature":"19.6","dtg":"2016-07-28 12:46:00"},{"temperature":"19.6","dtg":"2016-07-28 12:45:00"},{"temperature":"19.6","dtg":"2016-07-28 12:44:00"},{"temperature":"19.7","dtg":"2016-07-28 12:43:00"},{"temperature":"19.7","dtg":"2016-07-28 12:42:00"},{"temperature":"19.7","dtg":"2016-07-28 12:41:00"},{"temperature":"19.7","dtg":"2016-07-28 12:40:00"},{"temperature":"19.7","dtg":"2016-07-28 12:39:00"},{"temperature":"19.7","dtg":"2016-07-28 12:38:00"},{"temperature":"19.8","dtg":"2016-07-28 12:37:00"},{"temperature":"19.8","dtg":"2016-07-28 12:36:00"},{"temperature":"19.8","dtg":"2016-07-28 12:35:00"},{"temperature":"19.8","dtg":"2016-07-28 12:34:00"},{"temperature":"19.8","dtg":"2016-07-28 12:33:00"},{"temperature":"19.8","dtg":"2016-07-28 12:32:00"},{"temperature":"19.8","dtg":"2016-07-28 12:31:00"},{"temperature":"19.8","dtg":"2016-07-28 12:30:00"},{"temperature":"19.9","dtg":"2016-07-28 12:29:00"},{"temperature":"19.9","dtg":"2016-07-28 12:28:00"},{"temperature":"19.9","dtg":"2016-07-28 12:27:00"},{"temperature":"19.9","dtg":"2016-07-28 12:26:00"},{"temperature":"19.9","dtg":"2016-07-28 12:25:00"},{"temperature":"19.9","dtg":"2016-07-28 12:24:00"},{"temperature":"20.0","dtg":"2016-07-28 12:23:00"},{"temperature":"20.0","dtg":"2016-07-28 12:22:00"},{"temperature":"20.1","dtg":"2016-07-28 12:21:00"},{"temperature":"20.1","dtg":"2016-07-28 12:20:00"},{"temperature":"20.1","dtg":"2016-07-28 12:19:00"},{"temperature":"20.0","dtg":"2016-07-28 12:18:00"},{"temperature":"20.0","dtg":"2016-07-28 12:17:00"},{"temperature":"20.0","dtg":"2016-07-28 12:16:00"},{"temperature":"20.0","dtg":"2016-07-28 12:15:00"},{"temperature":"20.0","dtg":"2016-07-28 12:14:00"},{"temperature":"20.0","dtg":"2016-07-28 12:13:00"},{"temperature":"20.0","dtg":"2016-07-28 12:12:00"},{"temperature":"20.0","dtg":"2016-07-28 12:11:00"},{"temperature":"19.9","dtg":"2016-07-28 12:10:00"},{"temperature":"20.0","dtg":"2016-07-28 12:09:00"},{"temperature":"20.0","dtg":"2016-07-28 12:08:00"},{"temperature":"20.0","dtg":"2016-07-28 12:07:00"},{"temperature":"20.0","dtg":"2016-07-28 12:06:00"},{"temperature":"19.9","dtg":"2016-07-28 12:05:00"},{"temperature":"19.9","dtg":"2016-07-28 12:04:00"},{"temperature":"19.9","dtg":"2016-07-28 12:03:00"},{"temperature":"19.9","dtg":"2016-07-28 12:02:00"},{"temperature":"19.9","dtg":"2016-07-28 12:01:00"},{"temperature":"19.9","dtg":"2016-07-28 12:00:00"},{"temperature":"19.9","dtg":"2016-07-28 11:59:00"},{"temperature":"19.9","dtg":"2016-07-28 11:58:00"},{"temperature":"19.8","dtg":"2016-07-28 11:57:00"},{"temperature":"19.8","dtg":"2016-07-28 11:56:00"},{"temperature":"19.8","dtg":"2016-07-28 11:55:00"},{"temperature":"19.8","dtg":"2016-07-28 11:54:00"},{"temperature":"19.8","dtg":"2016-07-28 11:53:00"},{"temperature":"19.7","dtg":"2016-07-28 11:52:00"},{"temperature":"19.7","dtg":"2016-07-28 11:51:00"},{"temperature":"19.7","dtg":"2016-07-28 11:50:00"},{"temperature":"19.7","dtg":"2016-07-28 11:49:00"},{"temperature":"19.7","dtg":"2016-07-28 11:48:00"},{"temperature":"19.7","dtg":"2016-07-28 11:47:00"},{"temperature":"19.6","dtg":"2016-07-28 11:46:00"},{"temperature":"19.7","dtg":"2016-07-28 11:45:00"},{"temperature":"19.6","dtg":"2016-07-28 11:44:00"},{"temperature":"19.6","dtg":"2016-07-28 11:43:00"},{"temperature":"19.6","dtg":"2016-07-28 11:42:00"},{"temperature":"19.6","dtg":"2016-07-28 11:41:00"},{"temperature":"19.6","dtg":"2016-07-28 11:40:00"},{"temperature":"19.6","dtg":"2016-07-28 11:39:00"},{"temperature":"19.6","dtg":"2016-07-28 11:38:00"},{"temperature":"19.6","dtg":"2016-07-28 11:37:00"},{"temperature":"19.6","dtg":"2016-07-28 11:36:00"},{"temperature":"19.6","dtg":"2016-07-28 11:35:00"},{"temperature":"19.6","dtg":"2016-07-28 11:34:00"},{"temperature":"19.5","dtg":"2016-07-28 11:33:00"},{"temperature":"19.5","dtg":"2016-07-28 11:32:00"},{"temperature":"19.5","dtg":"2016-07-28 11:31:00"},{"temperature":"19.5","dtg":"2016-07-28 11:30:00"},{"temperature":"19.5","dtg":"2016-07-28 11:29:00"},{"temperature":"19.5","dtg":"2016-07-28 11:28:00"},{"temperature":"19.5","dtg":"2016-07-28 11:27:00"},{"temperature":"19.5","dtg":"2016-07-28 11:26:00"},{"temperature":"19.5","dtg":"2016-07-28 11:25:00"},{"temperature":"19.5","dtg":"2016-07-28 11:24:00"},{"temperature":"19.4","dtg":"2016-07-28 11:23:00"},{"temperature":"19.4","dtg":"2016-07-28 11:22:00"},{"temperature":"19.4","dtg":"2016-07-28 11:21:00"},{"temperature":"19.4","dtg":"2016-07-28 11:20:00"},{"temperature":"19.4","dtg":"2016-07-28 11:19:00"},{"temperature":"19.4","dtg":"2016-07-28 11:18:00"},{"temperature":"19.4","dtg":"2016-07-28 11:17:00"},{"temperature":"19.4","dtg":"2016-07-28 11:16:00"},{"temperature":"19.4","dtg":"2016-07-28 11:15:00"},{"temperature":"19.4","dtg":"2016-07-28 11:14:00"},{"temperature":"19.3","dtg":"2016-07-28 11:13:00"},{"temperature":"19.3","dtg":"2016-07-28 11:12:00"},{"temperature":"19.3","dtg":"2016-07-28 11:11:00"},{"temperature":"19.3","dtg":"2016-07-28 11:10:00"},{"temperature":"19.3","dtg":"2016-07-28 11:09:00"},{"temperature":"19.3","dtg":"2016-07-28 11:08:00"},{"temperature":"19.3","dtg":"2016-07-28 11:07:00"},{"temperature":"19.3","dtg":"2016-07-28 11:06:00"},{"temperature":"19.3","dtg":"2016-07-28 11:05:00"},{"temperature":"19.3","dtg":"2016-07-28 11:04:00"},{"temperature":"19.2","dtg":"2016-07-28 11:03:00"},{"temperature":"19.2","dtg":"2016-07-28 11:02:00"},{"temperature":"19.2","dtg":"2016-07-28 11:01:00"},{"temperature":"19.2","dtg":"2016-07-28 11:00:00"},{"temperature":"19.2","dtg":"2016-07-28 10:59:00"},{"temperature":"19.2","dtg":"2016-07-28 10:58:00"},{"temperature":"19.2","dtg":"2016-07-28 10:57:00"},{"temperature":"19.2","dtg":"2016-07-28 10:56:00"},{"temperature":"19.1","dtg":"2016-07-28 10:55:00"},{"temperature":"19.1","dtg":"2016-07-28 10:54:00"},{"temperature":"19.1","dtg":"2016-07-28 10:53:00"},{"temperature":"19.1","dtg":"2016-07-28 10:52:00"},{"temperature":"19.1","dtg":"2016-07-28 10:51:00"},{"temperature":"19.1","dtg":"2016-07-28 10:50:00"},{"temperature":"19.1","dtg":"2016-07-28 10:49:00"},{"temperature":"19.1","dtg":"2016-07-28 10:48:00"},{"temperature":"19.1","dtg":"2016-07-28 10:47:00"},{"temperature":"19.1","dtg":"2016-07-28 10:46:00"},{"temperature":"19.1","dtg":"2016-07-28 10:45:00"},{"temperature":"19.0","dtg":"2016-07-28 10:44:00"},{"temperature":"19.0","dtg":"2016-07-28 10:43:00"},{"temperature":"19.0","dtg":"2016-07-28 10:42:00"},{"temperature":"19.0","dtg":"2016-07-28 10:41:00"}];

//plot
$(document).ready(function () {
    $.plot($("#placeholder"),  dataset1  );
});

flot图表网格显示在php页面的占位符中，但没有显示数据。

如果我使用以下格式将数据硬编码到变量dataset1中，则会出现图形。

[[1,300]，[2,600]，[3,550]，[4,400]，[5,300]];

我认为问题可能是由于我在php部分中对json数据进行了格式化，因此需要将其格式化为flot graph plotting。

我很抱歉，因为我是flot图表的新手并且在我发布这个问题（我的第一个这里）之前尝试了stackoverflow中的许多类似解决方案，但没有成功。任何帮助将不胜感激！

Answer 1

Flot期望您的数据集采用与您传入的数据格式不同的格式。我通过循环您当前的数据集（您的上一个示例）将其设置为正确的格式。

＆＃13;

var dataset1 = [{"temperature":"19.6","dtg":"2016-07-28 12:53:00"},{"temperature":"19.5","dtg":"2016-07-28 12:52:00"},{"temperature":"19.5","dtg":"2016-07-28 12:51:00"},{"temperature":"19.6","dtg":"2016-07-28 12:50:00"},{"temperature":"19.6","dtg":"2016-07-28 12:49:00"},{"temperature":"19.6","dtg":"2016-07-28 12:48:00"},{"temperature":"19.6","dtg":"2016-07-28 12:47:00"},{"temperature":"19.6","dtg":"2016-07-28 12:46:00"},{"temperature":"19.6","dtg":"2016-07-28 12:45:00"},{"temperature":"19.6","dtg":"2016-07-28 12:44:00"},{"temperature":"19.7","dtg":"2016-07-28 12:43:00"},{"temperature":"19.7","dtg":"2016-07-28 12:42:00"},{"temperature":"19.7","dtg":"2016-07-28 12:41:00"},{"temperature":"19.7","dtg":"2016-07-28 12:40:00"},{"temperature":"19.7","dtg":"2016-07-28 12:39:00"},{"temperature":"19.7","dtg":"2016-07-28 12:38:00"},{"temperature":"19.8","dtg":"2016-07-28 12:37:00"},{"temperature":"19.8","dtg":"2016-07-28 12:36:00"},{"temperature":"19.8","dtg":"2016-07-28 12:35:00"},{"temperature":"19.8","dtg":"2016-07-28 12:34:00"},{"temperature":"19.8","dtg":"2016-07-28 12:33:00"},{"temperature":"19.8","dtg":"2016-07-28 12:32:00"},{"temperature":"19.8","dtg":"2016-07-28 12:31:00"},{"temperature":"19.8","dtg":"2016-07-28 12:30:00"},{"temperature":"19.9","dtg":"2016-07-28 12:29:00"},{"temperature":"19.9","dtg":"2016-07-28 12:28:00"},{"temperature":"19.9","dtg":"2016-07-28 12:27:00"},{"temperature":"19.9","dtg":"2016-07-28 12:26:00"},{"temperature":"19.9","dtg":"2016-07-28 12:25:00"},{"temperature":"19.9","dtg":"2016-07-28 12:24:00"},{"temperature":"20.0","dtg":"2016-07-28 12:23:00"},{"temperature":"20.0","dtg":"2016-07-28 12:22:00"},{"temperature":"20.1","dtg":"2016-07-28 12:21:00"},{"temperature":"20.1","dtg":"2016-07-28 12:20:00"},{"temperature":"20.1","dtg":"2016-07-28 12:19:00"},{"temperature":"20.0","dtg":"2016-07-28 12:18:00"},{"temperature":"20.0","dtg":"2016-07-28 12:17:00"},{"temperature":"20.0","dtg":"2016-07-28 12:16:00"},{"temperature":"20.0","dtg":"2016-07-28 12:15:00"},{"temperature":"20.0","dtg":"2016-07-28 12:14:00"},{"temperature":"20.0","dtg":"2016-07-28 12:13:00"},{"temperature":"20.0","dtg":"2016-07-28 12:12:00"},{"temperature":"20.0","dtg":"2016-07-28 12:11:00"},{"temperature":"19.9","dtg":"2016-07-28 12:10:00"},{"temperature":"20.0","dtg":"2016-07-28 12:09:00"},{"temperature":"20.0","dtg":"2016-07-28 12:08:00"},{"temperature":"20.0","dtg":"2016-07-28 12:07:00"},{"temperature":"20.0","dtg":"2016-07-28 12:06:00"},{"temperature":"19.9","dtg":"2016-07-28 12:05:00"},{"temperature":"19.9","dtg":"2016-07-28 12:04:00"},{"temperature":"19.9","dtg":"2016-07-28 12:03:00"},{"temperature":"19.9","dtg":"2016-07-28 12:02:00"},{"temperature":"19.9","dtg":"2016-07-28 12:01:00"},{"temperature":"19.9","dtg":"2016-07-28 12:00:00"},{"temperature":"19.9","dtg":"2016-07-28 11:59:00"},{"temperature":"19.9","dtg":"2016-07-28 11:58:00"},{"temperature":"19.8","dtg":"2016-07-28 11:57:00"},{"temperature":"19.8","dtg":"2016-07-28 11:56:00"},{"temperature":"19.8","dtg":"2016-07-28 11:55:00"},{"temperature":"19.8","dtg":"2016-07-28 11:54:00"},{"temperature":"19.8","dtg":"2016-07-28 11:53:00"},{"temperature":"19.7","dtg":"2016-07-28 11:52:00"},{"temperature":"19.7","dtg":"2016-07-28 11:51:00"},{"temperature":"19.7","dtg":"2016-07-28 11:50:00"},{"temperature":"19.7","dtg":"2016-07-28 11:49:00"},{"temperature":"19.7","dtg":"2016-07-28 11:48:00"},{"temperature":"19.7","dtg":"2016-07-28 11:47:00"},{"temperature":"19.6","dtg":"2016-07-28 11:46:00"},{"temperature":"19.7","dtg":"2016-07-28 11:45:00"},{"temperature":"19.6","dtg":"2016-07-28 11:44:00"},{"temperature":"19.6","dtg":"2016-07-28 11:43:00"},{"temperature":"19.6","dtg":"2016-07-28 11:42:00"},{"temperature":"19.6","dtg":"2016-07-28 11:41:00"},{"temperature":"19.6","dtg":"2016-07-28 11:40:00"},{"temperature":"19.6","dtg":"2016-07-28 11:39:00"},{"temperature":"19.6","dtg":"2016-07-28 11:38:00"},{"temperature":"19.6","dtg":"2016-07-28 11:37:00"},{"temperature":"19.6","dtg":"2016-07-28 11:36:00"},{"temperature":"19.6","dtg":"2016-07-28 11:35:00"},{"temperature":"19.6","dtg":"2016-07-28 11:34:00"},{"temperature":"19.5","dtg":"2016-07-28 11:33:00"},{"temperature":"19.5","dtg":"2016-07-28 11:32:00"},{"temperature":"19.5","dtg":"2016-07-28 11:31:00"},{"temperature":"19.5","dtg":"2016-07-28 11:30:00"},{"temperature":"19.5","dtg":"2016-07-28 11:29:00"},{"temperature":"19.5","dtg":"2016-07-28 11:28:00"},{"temperature":"19.5","dtg":"2016-07-28 11:27:00"},{"temperature":"19.5","dtg":"2016-07-28 11:26:00"},{"temperature":"19.5","dtg":"2016-07-28 11:25:00"},{"temperature":"19.5","dtg":"2016-07-28 11:24:00"},{"temperature":"19.4","dtg":"2016-07-28 11:23:00"},{"temperature":"19.4","dtg":"2016-07-28 11:22:00"},{"temperature":"19.4","dtg":"2016-07-28 11:21:00"},{"temperature":"19.4","dtg":"2016-07-28 11:20:00"},{"temperature":"19.4","dtg":"2016-07-28 11:19:00"},{"temperature":"19.4","dtg":"2016-07-28 11:18:00"},{"temperature":"19.4","dtg":"2016-07-28 11:17:00"},{"temperature":"19.4","dtg":"2016-07-28 11:16:00"},{"temperature":"19.4","dtg":"2016-07-28 11:15:00"},{"temperature":"19.4","dtg":"2016-07-28 11:14:00"},{"temperature":"19.3","dtg":"2016-07-28 11:13:00"},{"temperature":"19.3","dtg":"2016-07-28 11:12:00"},{"temperature":"19.3","dtg":"2016-07-28 11:11:00"},{"temperature":"19.3","dtg":"2016-07-28 11:10:00"},{"temperature":"19.3","dtg":"2016-07-28 11:09:00"},{"temperature":"19.3","dtg":"2016-07-28 11:08:00"},{"temperature":"19.3","dtg":"2016-07-28 11:07:00"},{"temperature":"19.3","dtg":"2016-07-28 11:06:00"},{"temperature":"19.3","dtg":"2016-07-28 11:05:00"},{"temperature":"19.3","dtg":"2016-07-28 11:04:00"},{"temperature":"19.2","dtg":"2016-07-28 11:03:00"},{"temperature":"19.2","dtg":"2016-07-28 11:02:00"},{"temperature":"19.2","dtg":"2016-07-28 11:01:00"},{"temperature":"19.2","dtg":"2016-07-28 11:00:00"},{"temperature":"19.2","dtg":"2016-07-28 10:59:00"},{"temperature":"19.2","dtg":"2016-07-28 10:58:00"},{"temperature":"19.2","dtg":"2016-07-28 10:57:00"},{"temperature":"19.2","dtg":"2016-07-28 10:56:00"},{"temperature":"19.1","dtg":"2016-07-28 10:55:00"},{"temperature":"19.1","dtg":"2016-07-28 10:54:00"},{"temperature":"19.1","dtg":"2016-07-28 10:53:00"},{"temperature":"19.1","dtg":"2016-07-28 10:52:00"},{"temperature":"19.1","dtg":"2016-07-28 10:51:00"},{"temperature":"19.1","dtg":"2016-07-28 10:50:00"},{"temperature":"19.1","dtg":"2016-07-28 10:49:00"},{"temperature":"19.1","dtg":"2016-07-28 10:48:00"},{"temperature":"19.1","dtg":"2016-07-28 10:47:00"},{"temperature":"19.1","dtg":"2016-07-28 10:46:00"},{"temperature":"19.1","dtg":"2016-07-28 10:45:00"},{"temperature":"19.0","dtg":"2016-07-28 10:44:00"},{"temperature":"19.0","dtg":"2016-07-28 10:43:00"},{"temperature":"19.0","dtg":"2016-07-28 10:42:00"},{"temperature":"19.0","dtg":"2016-07-28 10:41:00"}];

var dataset2 = [];
for (var i = 0; i < dataset1.length; i++) {
    dataset2.push( [ Date.parse(dataset1[i].dtg), 
	             parseFloat(dataset1[i].temperature) ] );
}
			
//plot
$(document).ready(function () {
    $.plot( $("#placeholder"),
            [dataset2], // wrap data series in a container
            { xaxis: { mode: "time" } }
    );
});

＆＃13;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/flot/0.7/jquery.flot.min.js"></script>
<div id="placeholder" style="width:600px; height:400px; float: left;"></div>

＆＃13;

在var dataset2 = [];之后，循环解包数据集中的每个元素，并创建一个[date, temp]数据点以添加到数组中。我不得不解析日期和浮动，因为Flot期望数字数据，而不是字符串。

创建一个数据系列。您可以在Flot中绘制多个数据系列，因此请注意我必须在调用plot的时候将该系列包装在另一个容器中。（换句话说，该容器可能有[dataset2, dataset3, ..., datasetX]。）

最后一步是在x轴上设置{ mode: "time" }。

格式化flot图数组的json数据

1 个答案: