Question

我正在尝试在y轴上绘制一个值为'IV'的简单折线图，并在x轴上绘制'Time'。我从MySQL数据库中读取这些值。这是我正在使用的PHP代码：

<?php
    $username = "root"; 
    $password = "root";   
    $host = "localhost";
    $database="db";

    $server = mysql_connect($host, $username, $password);
    $connection = mysql_select_db($database, $server);

    $myquery = "SELECT  data.IV, data.Time FROM  data";
    $query = mysql_query($myquery);

    if ( ! $myquery ) {
        echo mysql_error();
        die;
    }

    $data = array();

    for ($x = 0; $x < mysql_num_rows($query); $x++) {
        $data[] = mysql_fetch_assoc($query);
    }

    echo json_encode($data);     

    mysql_close($server);
?>

以下是生成的JSON：

[{"IV":"230.8","Time":"15:01:17+22\r"},{"IV":"233.7","Time":"15:06:57+22\r"},{"IV":"230.8","Time":"15:36:25+22\r"},{"IV":"234.5","Time":"15:40:38+22\r"},{"IV":"238.7","Time":"15:41:39+22\r"},{"IV":"238.7","Time":"15:41:50+22\r"},{"IV":"238.7","Time":"15:43:05+22\r"},{"IV":"230.8","Time":"15:01:17+22"},{"IV":"223.8","Time":"15:52:17+22"}]

所以我修改了我在网上找到的例子来尝试渲染数据。但是我得到的只是一个空白页面。这是我的代码，有人可以告诉我，我做错了什么？我已经坚持了几天。

<!DOCTYPE html>
<meta charset="utf-8">
<style> /* set the CSS */

body { font: 12px Arial;}

path { 
    stroke: steelblue;
    stroke-width: 2;
    fill: none;
}

.axis path,
.axis line {
    fill: none;
    stroke: grey;
    stroke-width: 1;
    shape-rendering: crispEdges;
}

</style>
<body>

<!-- load the d3.js library --> 
<script type="text/javascript" src="d3/d3.v3.js"></script>

<script>

// Set the dimensions of the canvas / graph
var margin = {top: 30, right: 20, bottom: 30, left: 50},
    width = 600 - margin.left - margin.right,
    height = 270 - margin.top - margin.bottom;

// Set the ranges
var x = d3.time.scale().range([0, width]);
var y = d3.scale.linear().range([height, 0]);

// Define the axes
var xAxis = d3.svg.axis().scale(x)
    .orient("bottom").ticks(5);

var yAxis = d3.svg.axis().scale(y)
    .orient("left").ticks(5);

// Define the line
var valueline = d3.svg.line()
    .x(function(d) { return x(d.IV); })
    .y(function(d) { return y(d.Time); });

// Adds the svg canvas
var svg = d3.select("body")
    .append("svg")
        .attr("width", width + margin.left + margin.right)
        .attr("height", height + margin.top + margin.bottom)
    .append("g")
        .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

// Get the data
d3.json("gj.php", function(error, data) {
    data.forEach(function(d) {
        d.IV = +d.IV;
                d.Time = +d.Time;
    });

    // Scale the range of the data
    x.domain(d3.extent(data, function(d) { return d.IV; }));
    y.domain([0, d3.max(data, function(d) { return d.Time; })]);

    // Add the valueline path.
    svg.append("path")      // Add the valueline path.
        .attr("class", "line")
        .attr("d", valueline(data));

    // Add the X Axis
    svg.append("g")         // Add the X Axis
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis);

    // Add the Y Axis
    svg.append("g")         // Add the Y Axis
        .attr("class", "y axis")
        .call(yAxis);

});

</script>
</body>

以下是我可以看到的截图： enter image description here

我怀疑问题是在时间结束时存在+（数字）\ r \ n。但是，我需要使用这种格式的数据。

Answer 1

如果在尝试将时间强制转换为数字后对数据阵列执行console.log，则会看到每个对象上的Time属性为NaN，这会阻止其呈现。查看d3的时间格式化函数，在转换为数字之前将数字字符串解析为实际的javascript日期对象。

https://github.com/mbostock/d3/wiki/Time-Formatting

无法通过使用JSON从MySQL读取数据来在d3.js中呈现简单的图形

1 个答案: