Trend computation test

author(s): Øystein Moseng

by oysteinmoseng

HTML

<script src="https://code.highcharts.com/highcharts.js"></script>
<script src="https://code.highcharts.com/modules/exporting.js"></script>
<script src="https://code.highcharts.com/modules/export-data.js"></script>
<script src="https://code.highcharts.com/modules/accessibility.js"></script>

<fieldset>
    <legend>
        Chart data
    </legend>
    <label class="datasel">
       Dataset 1
       <input type="radio" name="dataset" value="1" checked>
    </label>
    <label class="datasel">
       Dataset 2
       <input type="radio" name="dataset" value="2">
    </label>
    <label class="datasel">
       Dataset 3
       <input type="radio" name="dataset" value="3">
    </label>
    <label class="datasel">
       Dataset 4
       <input type="radio" name="dataset" value="4">
    </label>
    <label class="datasel">
       Dataset 5
       <input type="radio" name="dataset" value="5">
    </label>
    <label style="display: none">
       Random
       <input id="random" type="radio" name="dataset" value="random">
    </label>
    <button id="randomize">
        Randomize
    </button>
</fieldset>
<figure class="highcharts-figure">
    <div id="container"></div>
    <p class="highcharts-description" id="trend">Placeholder for trend</p>
</figure>
<div>
    <p>
        Fluctuation: <span id="fluctuation"></span>
    </p>
    <p>
        Trend coherence: <span id="coherence"></span>
    </p>
</div>

CSS

body {
    font-family: Verdana, sans-serif;    
}

.datasel {
    margin-right: 20px;    
}

.highcharts-figure, .highcharts-data-table table {
    min-width: 360px; 
    max-width: 800px;
    margin: 1em auto;
}

.highcharts-data-table table {
	border-collapse: collapse;
	border: 1px solid #EBEBEB;
	margin: 10px auto;
	text-align: center;
	width: 100%;
	max-width: 500px;
}
.highcharts-data-table caption {
    padding: 1em 0;
    font-size: 1.2em;
    color: #555;
}
.highcharts-data-table th {
	font-weight: 600;
    padding: 0.5em;
}
.highcharts-data-table td, .highcharts-data-table th, .highcharts-data-table caption {
    padding: 0.5em;
}
.highcharts-data-table thead tr, .highcharts-data-table tr:nth-child(even) {
    background: #f8f8f8;
}
.highcharts-data-table tr:hover {
    background: #f1f7ff;
}

JavaScript

function computeTrend(chart) {
	const dataRange = chart.series[0].dataMax - chart.series[0].dataMin;

    const zigzagDeviation = dataRange * 0.25;
    const flatDeviation = dataRange * 0.05;

	const points = chart.series[0].points;
    const len = points.length;
    const firstPoint = points[0];
    const lastPoint = points[len - 1];
	const poiList = [];
    let mode = 0;
    let candidateFlat = null;
    let numFlats = 0;
    let candidateHigh = null;
    let candidateLow = null;
	let lastAddedPoint = firstPoint;
    let lastCandidatePoint = firstPoint;

	for (let i = 1; i < len; ++i) {
		const point = points[i];
        const isLast = i === len - 1;

        if (mode === 0) {
        	// Flat
            const deviation = point.y - lastAddedPoint.y;
            const isHighCandidate = deviation > zigzagDeviation;
            const isLowCandidate = deviation < zigzagDeviation;
            const isFlatCandidate = Math.abs(deviation) < flatDeviation;
            
            if (isFlatCandidate) {
            	candidateFlat = lastCandidatePoint = point;
                numFlats++;
            } else if (candidateFlat) {
            	if (numFlats > 3) {
	                poiList.push([candidateFlat.x, candidateFlat.y]);
                    lastAddedPoint = lastCandidatePoint = point;
                }
                numFlats = 0;
				candidateFlat = null;
            }
            
            if (isLowCandidate) {
            	candidateLow = lastCandidatePoint = point;
            	mode = -1;
            }
            
            if (isHighCandidate) {
            	candidateHigh = lastCandidatePoint = point;
            	mode = 1;
            }

        } else if (mode === 1) {
        	// Rising
        	const deviation = point.y - lastCandidatePoint.y;
            const isHighCandidate = point.y > lastCandidatePoint.y;
            const isLowCandidate = deviation < zigzagDeviation;
            const isFlatCandidate = Math.abs(deviation) < flatDeviation;
      ...