CODEWITHSUNDEEP
javascriptdygraphs
Christoph Larndorfer
Christoph Larndorfer

Reputation: 71

Dygraph dynamic update legend values disappear

I am using a dygraph to monitor a CSV file and use the dynamic update function. When I hover over the graph to show the values of the curves in the legend, they disappear as soon as the graph is updated, which is a bit annoying.

<html>
<head>
<script type="text/javascript" src="/static/dygraph-combined.js"></script></head>
<body>
<div id="psu"></div>
<script type="text/javascript">
   g = new Dygraph(document.getElementById("psu"), "/data/psu", 
    {
        legend: 'always',
        hideOverlayOnMouseOut: false,
        ylabel: 'current (A)',
        height: 480,
        width: 640,
        sigFigs: 2,
        title: 'power interface monitor',
        xValueFormatter: Dygraph.dateString_,
        xAxisLabelFormatter: Dygraph.dateString_,
        xTicker: Dygraph.dateTicker
    } );
   window.intervalId = setInterval(function(){g.updateOptions( { 'file': "/data/psu" } ); }, 1000);
</script>
</html>

So the graph is all displaying correctly and the data is updated, only the legend values disappear after the graph is refreshed with g.updateOptions(). I was thinking maybe I can re-trigger some kind of "mouseover" event after g.updateOptions() so the values come back, but there might be a cleaner way of doing it.

Thanks.

Upvotes: 4

Views: 840

Answers (1)

Christoph Larndorfer
Christoph Larndorfer

Reputation: 71

I found a solution to my problem, but I am not sure how well it is implemented. I share it here so others might find it:

 $(document).ready(function() {
   var data = [];
   var t = new Date();
   for (var i = 10; i >= 0; i--) {
     var x = new Date(t.getTime() - i * 1000);
     data.push([x, Math.random()]);
   }

   var last_mousemove_evt = null;
   var on_graph = false;

   var g = new Dygraph(document.getElementById("div_g"), data, {
     legend: 'always',
     drawPoints: true,
     showRoller: true,
     valueRange: [0.0, 1.2],
     labels: ['Time', 'Random'],
     highlightCallback: function(e, x, pts, row) {
       last_mousemove_evt = e;
       on_graph = true
     },
     unhighlightCallback: function(e) {
       on_graph = false;
     }
   });
   // It sucks that these things aren't objects, and we need to store state in window.
   window.intervalId = setInterval(function() {
     var x = new Date(); // current time
     var y = Math.random();
     data.push([x, y]);
     g.updateOptions({
       'file': data
     });
     if (on_graph) {
       g.mouseMove_(last_mousemove_evt);
     }
   }, 1000);
 });
<script src="https://cdnjs.cloudflare.com/ajax/libs/dygraph/1.1.1/dygraph-combined.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js"></script>
<div id="div_g" style="width:600px; height:300px;"></div>

So I end up using the highlightCallback and unhighlightCallback options so I can figure out the mouse position and after a dynamic update call then the dygraph.mouseMove_() function to redraw the legend values. Seems to work.

Please let me know if there is a nicer solution around. Might be good to include this functionality in the dygraph.updateOptions() by default, as it seems weird that the legend values disappear after an update.

Upvotes: 3

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