An SVG Line with a simple look
Here is a simple Line chart
that has three separate datasets. The labels
for the chart (on the x-axis
) are not a scale - they're just regular labels
as you would normally give to a Line chart
but they're numbers instead
of words - that's all. The Line doesn't have the facility to show
a scale across the x-axis
- for that you'll need to use a Scatter chart
with the line
option enabled.
As for the tickmarks, while at first glance it may appear that they're 'hollow' they're actually just using a fill color that matches the background.
Other than this it's a pretty basic dark-themed Line that uses the
trace
effect.
<script src="RGraph.svg.common.core.js"></script> <script src="RGraph.svg.line.js"></script>Put this where you want the chart to show up:
<div style="float: right"> <div id="cc" style="width:700px; height: 300px; background-color: black"></div> </div>This is the code that generates the chart - it should be placed AFTER the
div
tag:
<script> line = new RGraph.SVG.Line({ id: 'cc', data: [ [9,9,0,9,0], [6,7,10,5,0], [9,4,0,3,4] ], options: { colors: ['#cc0','blue','red'], xaxis: false, yaxis: false, linewidth: 3, backgroundGridColor: '#999', xaxisLabels: ['5.0','6.0','7.0','8.0','9.0'], textColor: '#ccc', tickmarksStyle: 'circle', tickmarksFill: 'black', tickmarksLinewidth: 3, responsive: [ {maxWidth:null,width:700,height:300,options:{textSize: 12,tickmarksSize:5},css:{'float':'right'}}, {maxWidth:800,width:450,height:200,options:{textSize: 10,tickmarksSize:4},css:{'float':'none'}} ] } }).trace(); </script>
How to get transparent tickmarks using the canvas Line chart
You may have noticed that on the chart above the center of the tickmarks are not transparent - they're just colored black in order to make them blend in with the rest of the chart.
Making them transparent is more complicated than you might think for these reasons:
- If you use a transparent fill then the Line itself would still be visible.
- If you use a black fill it overwrites the background grid (this is the first chart).
-
If you use the
globalCompositeOperation
option but with only onecanvas
it clears the background grid - so the line can't be seen and nor can the grid. The result would be similar to the first situation in this list.
The solution here is to use layers. "But wait! canvas
doesn't have layers!"
you might cry. And yes - you would be correct - but they can be simulated
by using - in this case - multiple canvas
tags.
So there are two canvas
tags being utilised here (positioned one in front of
the other) - one on to which the background is drawn and a second on to
which the lines are drawn. When the insides of the tickmarks are cleared
to transparency then the canvas
at the back shows through. And that
is the canvas
that has the background grid on it.
There's more code required than a regular chart (as you might imagine) - but as you can see it's not a lot more and nor is it complicated. Feel free to copy and paste the code.
This goes in the documents header:
<script src="RGraph.common.core.js"></script> <script src="RGraph.line.js"></script>Put this where you want the chart to show up:
<div style="position: relative; background-color: black; width: 650px; height: 250px"> <canvas id="cvs1" width="750" height="250" style="position: absolute; top: 0; left: 0">[No canvas support]</canvas> <canvas id="cvs2" width="750" height="250" style="position: absolute; top: 0; left: 0">[No canvas support]</canvas> </div>This is the code that generates the chart - it should be placed AFTER the
div
tag:
<script> line1 = new RGraph.Line({ id: 'cvs1', data: [null,null,null,null,null], options: { xaxis: false, yaxis: false, backgroundGridColor: '#999', yaxisLabels: false } }).on('beforedraw', function (obj) { RGraph.clear(obj.canvas, 'black'); }).draw(); line2 = new RGraph.Line({ id: 'cvs2', data: [ [9,9,0,9,0], [6,7,10,5,0], [9,4,0,3,4] ], options: { colors: ['#cc0','blue','red'], xaxis: false, yaxis: false, linewidth: 3, backgroundGrid: false, xaxisLabels: ['5.0','6.0','7.0','8.0','9.0'], textColor: '#ccc', tickmarksSize: 6, tickmarksStyle: function (obj, data, value, index, x, y, color, prevX, prevY) { // Draw the fill of the tickmark obj.path( 'gco destination-out b a % % % 0 6.29 false f red s % gco source-over', x, y, obj.get('tickmarksSize') - 1, color ); // This draws the outline of the tickmark obj.path( 'b lw 2 a % % % 0 6.29 false s %', x, y, obj.get('tickmarksSize'), color ); }, tickmarkSize: 6, responsive: [ {maxWidth:null,width:650,height:250,options:{textSize: 12,tickmarksSize:5},parentCss:{'float':'right'},callback:function (obj){var canvas = document.getElementById('cvs1');canvas.width = 650;canvas.height = 250;RGraph.cache = [];RGraph.redraw();}}, {maxWidth:800,width:450,height:200,options:{textSize: 10,tickmarksSize:4},parentCss:{'float':'none'},callback:function (obj){var canvas = document.getElementById('cvs1');canvas.width = 450;canvas.height = 200;RGraph.cache = [];RGraph.redraw();}} ] } }).draw(); </script>