samples/logisticmap.js

#// Usage: jjs -fx -scripting logisticmap.js -- <initial_x> <R>

/*
 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
 *
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 * modification, are permitted provided that the following conditions
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 *
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 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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// Logistic map viewer using Java8 Streams and JavaFX
// See also http://en.wikipedia.org/wiki/Logistic_map

if (!$OPTIONS._fx || arguments.length < 2) {
    print("Usage: jjs -fx -scripting logisticmap.js -- <initial_x> <R>");
    exit(1);
}

// parameters for the logistic map
var x = parseFloat(arguments[0]);
var R = parseFloat(arguments[1]);
var NUM_POINTS = arguments.length > 2? parseFloat(arguments[2]) : 20;

// Java classes used
var DoubleStream = Java.type('java.util.stream.DoubleStream');
var LineChart = Java.type("javafx.scene.chart.LineChart");
var NumberAxis = Java.type("javafx.scene.chart.NumberAxis");
var Scene = Java.type("javafx.scene.Scene");
var Stage = Java.type("javafx.stage.Stage");
var XYChart = Java.type("javafx.scene.chart.XYChart");

function start(stage) {
    stage.title = "Logistic Map: initial x = ${x}, R = ${R}";
    // make chart
    var xAxis = new NumberAxis();
    var yAxis = new NumberAxis();
    var lineChart = new LineChart(xAxis, yAxis);
    xAxis.setLabel("iteration");
    yAxis.setLabel("x");
    // make chart data series
    var series = new XYChart.Series();
    var data = series.data;
    // populate data using logistic iteration
    var i = 0;
    DoubleStream
        .generate(function() x = R*x*(1-x))
        .limit(NUM_POINTS)
        .forEach(
            function(value) {
                data.add(new XYChart.Data(i, value));
                i++;
            }
         );
    // add to stage
    var scene = new Scene(lineChart, 800, 600);
    lineChart.data.add(series);
    stage.scene = scene;
    stage.show();
}