D3 - 在垂直条形图中的矩形顶部获取文本

问题描述

我正在做一个垂直条形图与D3成功。我还希望频率的值位于每个矩形的顶部。我能够得到完整的结构和矩形。但是，我看不到我的价值观在酒吧的顶部。有人可以帮助吗？

I am making a vertical bar chart with D3 successfully. I further want the value of frequency to lie on the top of each rectangle. I am able to get the complete structure and rectangles. But, I cannot see my values residing on top of the bars. Can someone help out?

SNIPPET：

 $  

The problem here is simple: you cannot append a text element inside a rect element.
  code>元素将在您检查DOM时显示，但这并不意味着它工作，并且没有文本实际上会在SVG中绘制。
The text element will show up when you inspect the DOM, but this doesn't mean that it works, and no text will be actually painted in the SVG.
看看这里，我在哪里解释你的问题： 

Have a look here, where I explain exactly your problem: Correctly appending an SVG element
因此，它应该是：
 g.selectAll(".text")
      .data(data)
      .enter()
      .append("text")
      .attr("dy", ".75em")
      .attr("y", function(d) { return y(d.frequency); })
      .attr("x", function(d) { return x(d.letter); })
      .attr("text-anchor", "middle")
      .text(function(d) { return d.frequency; });
请注意，我更改了
.text(function(d) { return y(d.frequency); });
这是没有意义的：
.text(function(d) { return d.frequency; });
以下是您的代码演示：
 
 
var data = [{
    "letter": "A",
    "frequency": "5.01"
}, {
    "letter": "B",
    "frequency": "7.80"
}, {
    "letter": "C",
    "frequency": "15.35"
}, {
    "letter": "D",
    "frequency": "22.70"
}, {
    "letter": "E",
    "frequency": "34.25"
}, {
    "letter": "F",
    "frequency": "10.21"
}, {
    "letter": "G",
    "frequency": "7.68"
}, ];


//Setting up of our svg with proper calculations 
var svg = d3.select("body")
    .append("svg").attr("width", 500).attr("height", 300);
var margin = {
    top: 40,
    right: 20,
    bottom: 40,
    left: 40
};
var width = svg.attr("width") - margin.left - margin.right;
var height = svg.attr("height") - margin.top - margin.bottom;

//Plotting our base area in svg in which chart will be shown 
var g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")");

//X and Y scaling 
var x = d3.scaleBand().rangeRound([0, width]).padding(0.4);
var y = d3.scaleLinear().rangeRound([height, 0]);

x.domain(data.map(function(d) {
    return d.letter;
}));
y.domain([0, d3.max(data, function(d) {
    return +d.frequency;
})]);

//Final Plotting 

//for x axis 
g.append("g")
    .call(d3.axisBottom(x))
    .attr("transform", "translate(0," + height + ")");

//for y axis 
g.append("g")
    .call(d3.axisLeft(y))
    .append("text").attr("transform", "rotate(-90)").attr("text-anchor", "end");

//for rectangles 
g.selectAll(".bar")
    .data(data)
    .enter()
    .append("rect")
    .attr("class", "bar")
    .attr("x", function(d) {
        return x(d.letter);
    })
    .attr("y", function(d) {
        return y(d.frequency);
    })
    .attr("width", x.bandwidth())
    .attr("height", function(d) {
        return height - y(d.frequency);
    });

g.selectAll(".text")
    .data(data)
    .enter()
    .append("text")
    .attr("dy", ".75em")
    .attr("y", function(d) {
        return y(d.frequency) - 16;
    })
    .attr("x", function(d) {
        return x(d.letter) + x.bandwidth() / 2;
    })
    .attr("text-anchor", "middle")
    .text(function(d) {
        return d.frequency;
    });
<script src="https://d3js.org/d3.v4.min.js"></script>
                        
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