CODEWITHSUNDEEP
javascriptdomchart.jschartjs-2.6.0
infodev
infodev

Reputation: 5235

Do not draw line on condition in ChartJS line chart

I would like not draw line between two dots when a condition is triggered.

I'm using chartjs a time line graph.

My condition is not to draw line when y value decreases so in this example when it passes from 7 to 1 

{x:3.5*3600, y:7},
Do not draw line between these two points
{x:4*3600, y:1},

Is it possible to do with chartjs line time graph ?

var canvas = document.getElementById('myChart');
var config = {
  "options": {
    "scales": {
      "xAxes": [
            {
              "type": 'time',
              "time": {
                "unit": 'minute',
                "unitStepSize": 60,

              },
              "distribution": 'linear',
              "bounds": 'ticks',
              "ticks": {
                "source": 'auto',
                "autoSkip": true,
                "stepSize": 10
              }
            }
          ],
    },
  },
  "data": {
  	"labels": ['2016-04-18T00:00:00Z', '2016-04-18T23:59:00Z'],
    "datasets": [
    {
      "label": "line",
      "type": "line",
      "backgroundColor": "#00b",
      "borderColor": "#00b",
      //"yAxisID": "axis4",
      "borderWidth": 1,
      "fill": false,
      "data": [
{x:"2016-04-18T01:00:00Z", y:1},
{x:"2016-04-18T04:00:00Z", y:2},
{x:"2016-04-18T06:00:00Z", y:3},
{x:"2016-04-18T08:00:00Z", y:7},
{x:"2016-04-18T10:00:00Z", y:1},
{x:"2016-04-18T14:00:00Z", y:3},

]
    },
    ]
  },

};
var myBarChart = Chart.Line(canvas, config);
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.0/Chart.bundle.min.js"></script>
<canvas id="myChart" width="400" height="200"></canvas>

Update I have tried to add {x:null,y:null} or null between the two items but I get this error

Error: 0 and 1461023970000 are too far apart with stepSize of 60 minute

In my options I have :

"data": [
  {x:"2016-04-18T01:00:00Z", y:1},
  {x:"2016-04-18T04:00:00Z", y:2},
  {x:"2016-04-18T06:00:00Z", y:3},
  {x:"2016-04-18T08:00:00Z", y:7},
  {x:null,y:null},
  {x:"2016-04-18T10:00:00Z", y:1},
  {x:"2016-04-18T14:00:00Z", y:3},
]

...

xAxes: [
    {
      type: 'time',
      time: {
        unit: 'minute',
        unitStepSize: 60,
        parser: function(date) {
          return moment(date).toLocaleString();
        }
      },
      distribution: 'linear',
      bounds: 'ticks',
      ticks: {
        source: 'auto',
        autoSkip: true,
        stepSize: 10
      }
    }
  ],

It's like chartjs considering null to be a big value

Upvotes: 1

Views: 1735

Answers (2)

J&#233;r&#233;mie L
J&#233;r&#233;mie L

Reputation: 775

As explained in the Chart.js documentation (see spanGaps), if spanGaps is falsy (as default), points with NaN data will create a break in the line.

So, the trick is to insert an empty point, as you tried to do. This empty point must be timestamped, with a timestamp between the two points defining the "hole" in the line:

"data": [
  {x:"2016-04-18T01:00:00Z", y:1},
  {x:"2016-04-18T04:00:00Z", y:2},
  {x:"2016-04-18T06:00:00Z", y:3},
  {x:"2016-04-18T08:00:00Z", y:7},
  {x:"2016-04-18T08:00:00Z", y:null}, // or NaN
  {x:"2016-04-18T10:00:00Z", y:1},
  {x:"2016-04-18T14:00:00Z", y:3},
]

See this fiddle as example: https://jsfiddle.net/t1s54gdh/

Upvotes: 3

Aabhushan Gautam
Aabhushan Gautam

Reputation: 228

Set y as null while still defining the x co-ordinate. 

"data": [
  {x:"2016-04-18T01:00:00Z", y:1},
  {x:"2016-04-18T04:00:00Z", y:2},
  {x:"2016-04-18T06:00:00Z", y:3},
  {x:"2016-04-18T08:00:00Z", y:7},
  {x:"2016-04-18T08:00:01Z", y:null},
  {x:"2016-04-18T10:00:00Z", y:1},
  {x:"2016-04-18T14:00:00Z", y:3},
]

Upvotes: 1

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