Bringing Matplotlib to the Browser

Visualizing Random Walks

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Visualizing Random Walks

This shows the use of transparent lines to visualize random walk data. Thre is also a custom plugin defined which causes lines to be highlighted when the mouse hovers over them. Use the toolbar buttons at the bottom-right of the plot to enable zooming and panning, and to reset the view.

Python source code: [download source: random_walk.py]

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()

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