D3.js density.thresholds()函数

density.thresholds()函数用于设置密度估计函数的阈值。如果给出了阈值，那么这会将阈值生成器设置为指定的函数或数组。如果未给出阈值，则此函数将默认阈值返回给轮廓生成器函数。

句法：

d3.contourDensity.x().y().thresholds([thresholds]);

参数：此函数采用上面给出的一个参数，如下所述。

• 阈值：此参数采用数组或函数。

返回值：此函数不返回任何内容。

下面给出了density.thresholds()函数的几个示例。

示例 1：

HTML

 
 
  
 
     
     
  
     
     
    
    
 
  
 
    GeeksforGeeks
      
     
  
        // append the svg object to the body.
        var svg = d3.select("body")
        .append("svg")
            .attr("width", 530)
            .attr("height", 480)
        .append("g")
            .attr("transform",
                "translate(" + 40 + ", " + -80 + ")");
  
        // read data
        d3.csv("./data.csv", function(data) {
              
        var y = d3.scaleLinear()
            .domain([2, 30])
            .range([ 300, 100 ]);
  
        var x = d3.scaleLinear()
            .domain([2, 22])
            .range([ 0, 200]);
  
  
        svg.append("g")
        .call(d3.axisLeft(y));
          
        svg.append("g")
            .attr("transform", "translate(0, " + 300 + ")")
            .call(d3.axisBottom(x));
  
        var density= d3.contourDensity()
            .y(function(d) { return y(d.y); })
            .x(function(d) { return x(d.x); })
            // Use of thresholds() Function
            .thresholds(3)
            (data)
  
        svg.selectAll("path")
            .data(density)
            .enter()
            .append("path")
            .attr("d", d3.geoPath())
            .attr("fill", "none")
            .attr("stroke", "green")
        });
  
        // Data for csv file
        // x, y, group
        // 9.45, 14.14, H
        // 9.1, 14.14, H
        // 9.9, 9.9, H
        // 9.6, 14.5, H
        // 9.1, 9.7, H
        // 14.7, 9.5, H
        // 7.9, 9.6, H
        // 14.7, 9.7, H
        // 9.45, 14.14, H
        // 12.1, 9.14, H
        // 7.5, 9, H
        // 14.5, 14.5, H
        // 9.45, 9.7, H
        // 14.45, 9.6, H
        // 9.5, 7.6, H
        // 9, 9.45, H
        // 14.7, 12, H
        // 9.7, 9.7, H
        // 9.6, 9, H
        // 12, 9, H
        // 9.45, 14.5, H
        // 9.9, 14.6, H
        // 12.7, 9.9, H
        // 9, 12.14, H
        // 9, 14.9, H
        // 9.5, 9.7, H
        // 9.7, 14.7, H
        // 9.9, 14.5, H
        // 14, 14.5, H
        // 7.9, 9, H
        // 9.9, 9.45, H
        // 9, 14.14, H
        // 14.7, 9.7, H
        // 14.5, 9.9, H
     

输出：

示例 2：

HTML

 
 
  
 
     
     
  
     
     
    
    
 
  
 
    GeeksforGeeks
      
     
  
        // append the svg object to the body.
        var svg = d3.select("body")
        .append("svg")
            .attr("width", 530)
            .attr("height", 480)
        .append("g")
            .attr("transform",
                "translate(" + 40 + ", " + -80 + ")");
  
        // read data
        d3.csv("./data.csv", function(data) {
              
        var y = d3.scaleLinear()
            .domain([2, 30])
            .range([ 300, 100 ]);
  
        var x = d3.scaleLinear()
            .domain([2, 22])
            .range([ 0, 200]);
  
  
        svg.append("g")
        .call(d3.axisLeft(y));
          
        svg.append("g")
            .attr("transform", "translate(0, " + 300 + ")")
            .call(d3.axisBottom(x));
  
        var density= d3.contourDensity()
            .y(function(d) { return y(d.y); })
            .x(function(d) { return x(d.x); })
            // Use of thresholds() Function
            .thresholds(50)
            (data)
  
        svg.selectAll("path")
            .data(density)
            .enter()
            .append("path")
            .attr("d", d3.geoPath())
            .attr("fill", "none")
            .attr("stroke", "green")
        });
  
        // Data for csv file
        // x, y, group
        // 9.45, 14.14, H
        // 9.1, 14.14, H
        // 9.9, 9.9, H
        // 9.6, 14.5, H
        // 9.1, 9.7, H
        // 14.7, 9.5, H
        // 7.9, 9.6, H
        // 14.7, 9.7, H
        // 9.45, 14.14, H
        // 12.1, 9.14, H
        // 7.5, 9, H
        // 14.5, 14.5, H
        // 9.45, 9.7, H
        // 14.45, 9.6, H
        // 9.5, 7.6, H
        // 9, 9.45, H
        // 14.7, 12, H
        // 9.7, 9.7, H
        // 9.6, 9, H
        // 12, 9, H
        // 9.45, 14.5, H
        // 9.9, 14.6, H
        // 12.7, 9.9, H
        // 9, 12.14, H
        // 9, 14.9, H
        // 9.5, 9.7, H
        // 9.7, 14.7, H
        // 9.9, 14.5, H
        // 14, 14.5, H
        // 7.9, 9, H
        // 9.9, 9.45, H
        // 9, 14.14, H
        // 14.7, 9.7, H
        // 14.5, 9.9, H
     

 

输出：