我是初学者，当我尝试在lineChart中选择一些元素时遇到了问题。 我知道有这么多精英，所以我来这里寻求帮助:) 我在there找到了一个画笔演示和一个折线图（抱歉他们不允许我插入2个链接，因为我没有10个声誉）演示然后我写代码打击：
<!DOCTYPE html>
<meta charset="utf-8">
<style type="text/css">
/* 13. Basic Styling with CSS */
/* Style the lines by removing the fill and applying a stroke */
.line {
fill: none;
stroke: #ffab00;
stroke-width: 3;
}
/* Style the dots by assigning a fill and stroke */
.dot {
fill: #1 fab40;
stroke: #fff;
}
.dot .selected {
stroke: red;
}
</style>
<!-- Body tag is where we will append our SVG and SVG objects-->
<body>
</body>
<!-- Load in the d3 library -->
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>
// 2. Use the margin convention practice
var margin = {top: 20, right: 50, bottom: 20, left: 50}
, width = window.innerWidth - margin.left - margin.right // Use the window's width
, height = window.innerHeight - margin.top - margin.bottom; // Use the window's height
// The number of datapoints
var n = 21;
// 5. X scale will use the index of our data
var xScale = d3.scaleLinear()
.domain([0, n-1]) // input
.range([0, width]); // output
// 6. Y scale will use the randomly generate number
var yScale = d3.scaleLinear()
.domain([0, 1]) // input
.range([height, 0]); // output
// 7. d3's line generator
var line = d3.line()
.x(function(d, i) { return xScale(i); }) // set the x values for the line generator
.y(function(d) { return yScale(d.y); }) // set the y values for the line generator
.curve(d3.curveMonotoneX);// apply smoothing to the line
// 8. An array of objects of length N. Each object has key -> value pair, the key being "y" and the value is a random number
var dataset = d3.range(n).map(function(d) { return {"y": d3.randomUniform(1)() } });
// 1. Add the SVG to the page and employ #2
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 + ")");
// 3. Call the x axis in a group tag
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(xScale)); // Create an axis component with d3.axisBottom
// 4. Call the y axis in a group tag
svg.append("g")
.attr("class", "y axis")
.call(d3.axisLeft(yScale)); // Create an axis component with d3.axisLeft
// 9. Append the path, bind the data, and call the line generator
svg.append("path")
.datum(dataset) // 10. Binds data to the line
.attr("class", "line") // Assign a class for styling
.attr("d", line); // 11. Calls the line generator
// 12. Appends a circle for each datapoint
var dot = svg.append("g")
.attr("class", "dot") // Assign a class for styling
.selectAll(".dot")
.data(dataset)
.enter().append("circle") // Uses the enter().append() method
.attr("r", 5)
.attr("cx", function(d, i) { return xScale(i) })
.attr("cy", function(d) { return yScale(d.y) });
var brush = svg.append("g")
.attr("class", "brush")
.call(d3.brush()
.extent([[0, 0], [width, height]])
.on("start brush end", brushed));
function brushed() {
var selection = d3.event.selection;
dot.classed("selected", selection && function(d) {
return selection[0][0] <= d.x && d.x < selection[1][0]
&& selection[0][1] <= d.y && d.y < selection[1][1];
});
}
</script>
我尝试编写像this demo这样的相同代码，但我无法选择任何一个点，问题在哪里？ 非常感谢！
答案 0 :(得分：1)
重写您的brushed功能，如下所示：
function brushed() {
var selection = d3.event.selection;
dot.classed("selected", selection && function(d,i) {
return selection[0][0] <= xScale(i) && xScale(i) < selection[1][0]
&& selection[0][1] <= yScale(d.y) && yScale(d.y) < selection[1][1];
});
}
注意，我们在这里使用xScale和yScale来正确匹配所选区域和点的坐标。工作示例如下：
// 2. Use the margin convention practice
var margin = {top: 20, right: 50, bottom: 20, left: 50}
, width = window.innerWidth - margin.left - margin.right // Use the window's width
, height = window.innerHeight - margin.top - margin.bottom; // Use the window's height
// The number of datapoints
var n = 21;
// 5. X scale will use the index of our data
var xScale = d3.scaleLinear()
.domain([0, n-1]) // input
.range([0, width]); // output
// 6. Y scale will use the randomly generate number
var yScale = d3.scaleLinear()
.domain([0, 1]) // input
.range([height, 0]); // output
// 7. d3's line generator
var line = d3.line()
.x(function(d, i) { return xScale(i); }) // set the x values for the line generator
.y(function(d) { return yScale(d.y); }) // set the y values for the line generator
.curve(d3.curveMonotoneX);// apply smoothing to the line
// 8. An array of objects of length N. Each object has key -> value pair, the key being "y" and the value is a random number
var dataset = d3.range(n).map(function(d) { return {"y": d3.randomUniform(1)() } });
// 1. Add the SVG to the page and employ #2
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 + ")");
// 3. Call the x axis in a group tag
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(xScale)); // Create an axis component with d3.axisBottom
// 4. Call the y axis in a group tag
svg.append("g")
.attr("class", "y axis")
.call(d3.axisLeft(yScale)); // Create an axis component with d3.axisLeft
// 9. Append the path, bind the data, and call the line generator
svg.append("path")
.datum(dataset) // 10. Binds data to the line
.attr("class", "line") // Assign a class for styling
.attr("d", line); // 11. Calls the line generator
// 12. Appends a circle for each datapoint
var dot = svg.append("g")
.attr("class", "dot") // Assign a class for styling
.selectAll(".dot")
.data(dataset)
.enter().append("circle") // Uses the enter().append() method
.attr("r", 5)
.attr("cx", function(d, i) { return xScale(i) })
.attr("cy", function(d) { return yScale(d.y) });
var brush = svg.append("g")
.attr("class", "brush")
.call(d3.brush()
.extent([[0, 0], [width, height]])
.on("start brush", brushed)
.on("end", getSelectedDots)
);
var selectedDots = [];
function getSelectedDots() {
var selection = d3.event.selection;
dot.classed("selected", selection && function(d,i) {
var isSelectedDot = selection[0][0] <= xScale(i) && xScale(i) < selection[1][0]
&& selection[0][1] <= yScale(d.y) && yScale(d.y) < selection[1][1];
if (isSelectedDot) {
selectedDots.push(d);
}
return isSelectedDot;
});
console.log('selectedDots ', selectedDots);
}
function brushed() {
var selection = d3.event.selection;
dot.classed("selected", selection && function(d,i) {
return selection[0][0] <= xScale(i) && xScale(i) < selection[1][0]
&& selection[0][1] <= yScale(d.y) && yScale(d.y) < selection[1][1];
});
}/* 13. Basic Styling with CSS */
/* Style the lines by removing the fill and applying a stroke */
.line {
fill: none;
stroke: #ffab00;
stroke-width: 3;
}
/* Style the dots by assigning a fill and stroke */
.dot {
fill: #1fab40;
stroke: #fff;
}
.dot .selected {
stroke: red;
}<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.11.0/d3.min.js"></script>