Highlighting lines on a random walk plot mpld3

Question

I have a table consisting of id , value columns and a corresponding [random walk plot][1] using mpld3. I would like to pre-highlight a particular line from the line plot instead of mouseover.

Code snippet from mpld3 : [1]: https://mpld3.github.io/examples/random_walk.html

import jinja2
import json
import numpy as np
import matplotlib.pyplot as plt
import mpld3
from mpld3 import plugins, utils

class HighlightLines(plugins.PluginBase):
    """A plugin to highlight lines on hover"""
    JAVASCRIPT = """
    mpld3.register_plugin("linehighlight", LineHighlightPlugin);
    LineHighlightPlugin.prototype = Object.create(mpld3.Plugin.prototype);
    LineHighlightPlugin.prototype.constructor = LineHighlightPlugin;
    LineHighlightPlugin.prototype.requiredProps = ["line_ids"];
    LineHighlightPlugin.prototype.defaultProps = {alpha_bg:0.3, alpha_fg:1.0}
    function LineHighlightPlugin(fig, props){
        mpld3.Plugin.call(this, fig, props);
    };

    LineHighlightPlugin.prototype.draw = function(){
      for(var i=0; i<this.props.line_ids.length; i++){
         var obj = mpld3.get_element(this.props.line_ids[i], this.fig),
             alpha_fg = this.props.alpha_fg;
             alpha_bg = this.props.alpha_bg;
         obj.elements()
             .on("mouseover", function(d, i){
                            d3.select(this).transition().duration(50)
                              .style("stroke-opacity", alpha_fg); })
             .on("mouseout", function(d, i){
                            d3.select(this).transition().duration(200)
                              .style("stroke-opacity", alpha_bg); });
      }
    };
    """

    def __init__(self, lines):
        self.lines = lines
        self.dict_ = {"type": "linehighlight",
                      "line_ids": [utils.get_id(line) for line in lines],
                      "alpha_bg": lines[0].get_alpha(),
                      "alpha_fg": 1.0}
    N_paths = 50
    N_steps = 100

    x = np.linspace(0, 10, 100)
    y = 0.1 * (np.random.random((N_paths, N_steps)) - 0.5)
    y = y.cumsum(1)

    fig, ax = plt.subplots(subplot_kw={'xticks': [], 'yticks': []})
    lines = ax.plot(x, y.T, color='blue', lw=4, alpha=0.1)
    plugins.connect(fig, HighlightLines(lines))

    mpld3.show()

Code after incorporating @codemax's suggestion

import jinja2
import json
import numpy as np
import matplotlib.pyplot as plt
import mpld3
from mpld3 import plugins, utils

class HighlightLines(plugins.PluginBase):
    """A plugin to highlight lines on hover"""
    JAVASCRIPT = """
    mpld3.register_plugin("linehighlight", LineHighlightPlugin);
    LineHighlightPlugin.prototype = Object.create(mpld3.Plugin.prototype);
    LineHighlightPlugin.prototype.constructor = LineHighlightPlugin;
    LineHighlightPlugin.prototype.requiredProps = ["line_ids"];
    LineHighlightPlugin.prototype.defaultProps = {alpha_bg:0.3, alpha_fg:1.0}
    function LineHighlightPlugin(fig, props){
        mpld3.Plugin.call(this, fig, props);
    };

    LineHighlightPlugin.prototype.draw = function(){
      for(var i=0; i<this.props.line_ids.length; i++){
         const list = [0, 4, 6];
         if (list.includes(i)) {
           obj.elements().style("stroke-opacity", alpha_fg);
         }
       }
    };
    """

    def __init__(self, lines):
        self.lines = lines
        self.dict_ = {"type": "linehighlight",
                      "line_ids": [utils.get_id(line) for line in lines],
                      "alpha_bg": lines[0].get_alpha(),
                      "alpha_fg": 1.0}
    N_paths = 50
    N_steps = 100

    x = np.linspace(0, 10, 100)
    y = 0.1 * (np.random.random((N_paths, N_steps)) - 0.5)
    y = y.cumsum(1)

    fig, ax = plt.subplots(subplot_kw={'xticks': [], 'yticks': []})
    lines = ax.plot(x, y.T, color='blue', lw=4, alpha=0.1)
    plugins.connect(fig, HighlightLines(lines))

    mpld3.show()

Answer 1

You can select individual lines and highlight it using this approach.

LineHighlightPlugin.prototype.draw = function(){
  for(var i=0; i<this.props.line_ids.length; i++){
      var obj = mpld3.get_element(this.props.line_ids[i], this.fig),
          alpha_fg = this.props.alpha_fg;
          alpha_bg = this.props.alpha_bg;
      // Depending on which line you wish to highlight, 
      // you can change 1 to any index 
      // add the following 3 lines to your code
      if (i === 1) {
        obj.elements().style("stroke-opacity", alpha_fg);
      }

      obj.elements()
          .on("mouseover", function(d, i){
                        d3.select(this).transition().duration(50)
                          .style("stroke-opacity", alpha_fg); })
          .on("mouseout", function(d, i){
                        d3.select(this).transition().duration(200)
                          .style("stroke-opacity", alpha_bg); });
  }
};

If you wish to highlight multiple lines, you can use this approach.

LineHighlightPlugin.prototype.draw = function(){
  for(var i=0; i<this.props.line_ids.length; i++){
      var obj = mpld3.get_element(this.props.line_ids[i], this.fig),
          alpha_fg = this.props.alpha_fg;
          alpha_bg = this.props.alpha_bg;
     // add the following 4 lines to your code
     const list = [0, 4, 6]; // these numbers are random. Use your own numbers
     if (list.includes(i)) {
       obj.elements().style("stroke-opacity", alpha_fg);
     }

      obj.elements()
          .on("mouseover", function(d, i){
                        d3.select(this).transition().duration(50)
                          .style("stroke-opacity", alpha_fg); })
          .on("mouseout", function(d, i){
                        d3.select(this).transition().duration(200)
                          .style("stroke-opacity", alpha_bg); });
  }
};