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RGraph is a JavaScript charts library based on HTML5 SVG and canvas. RGraph is mature (over 17 years old) and has a wealth of features making it an ideal choice to use for showing charts on your website.

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New HTML datagrid
In the April 2025 release a new datagrid object was added. This makes it easy to add static or dynamic data tables to your pages. It can be used whether you use the canvas or SVG libraries or entirely standalone.

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Get the latest version of RGraph (version 6.22, 24th June 2025) from the download page. You can read the changelog here. There's also older versions available, minified files and links to cdnjs.com hosted libraries.

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RGraph can be used for free under the GPL or if that doesn't suit your situation there's an inexpensive (£129) commercial license available.

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The drawing API Marker2 object API reference

The marker2 object allows you to add extra information to your charts in the form of markers. These markers can then give even more information in the form of tooltips or by using the event properties.

Usage example

<script>
    line = new RGraph.Line({
        id: 'cvs',
        data: [4,9,1,3,2,6,5],
        options: {
            spline: true,
            backgroundGridVlines:false,
            backgroundGridBorder:false,
            xaxis: false,
            yaxis: false,
            xaxisLabels: ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday'],
            marginInner: 5,
            tickmarksStyle: 'endcircle',
            tickmarksSize: 10,
            colors: ['black'],
            textSize: 16
        }
    }).draw();

    x = line.coords[3][0];
    y = line.coords[3][1];
    
    new RGraph.Drawing.Marker2({
        id: 'cvs',
        x: x,
        y: y,
        text: 'Note',
        options: {
            textSize: 18,
            tooltips: ['<b>Note</b><br />Extra information can be displayed'],
            tooltipsCss: {
                lineHeight: '15px',
                textAlign: 'left'
            },
            highlightFill: 'rgba(255,0,0,0.5)',
            shadow: false
        }
    }).draw();
</script>

Properties

Color properties

Name: colorsStroke
Description: 
The color used to stroke the circle.
Default: transparent
Name: colorsFill
Description: 
The color used to fill the circle.
Default: red

Text properties

Name: textFont
Description: 
This is the font that the text is rendered in.
Default: Arial, Verdana, sans-serif
Name: textSize
Description: 
The size of the text.
Default: 12
Name: textColor
Description: 
The color that the text is rendered in.
Default: black
Name: textBold
Description: 
Whether the text is bold or not.
Default: false
Name: textItalic
Description: 
Whether the text is italic or not.
Default: false
Name: textAccessible
Description: 
A new feature in 2016 that allows you to use dom text in place of canvas text. It makes for much higher quality text that you can also select if desired (for copy/paste operations). It won't fit all situations and you can read more about the DOM text feature here. A good way to control borders/margins/padding etc is not to set them on the canvas but to wrap the canvas in a div and set them on that like this:
<div style="margin-left: 50px; display: inline-block">
    <canvas id="cvs" width="650" height="250"></canvas>
</div>
Default: false
Name: text
Description: 
This allows you to add custom text to your chart if you want to. There's a dedicated page that describes this option here.
Default: null

Shadow properties

Name: shadow
Description: 
This controls whether the shadow is enabled or not.
Default: false
Name: shadowColor
Description: 
The color of the shadow.
Default: gray
Name: shadowOffsetx
Description: 
The X offset that the shadow is drawn at.
Default: 3
Name: shadowOffsety
Description: 
The Y offset that the shadow is drawn at.
Default: 3
Name: shadowBlur
Description: 
The severity of the shadow blur.
Default: 5

Interactive features properties

Name: tooltips
Description: 
The tooltip for the circle. Even though you can only have one - this should still be an array: obj.set('tooltips', ['The tooltip']);
Default: null
Name: tooltipsEvent
Description: 
This can be click or mousemove and controls what event is used to trigger the tooltip.
Default: click
Name: tooltipsHighlight
Description: 
This stipulates whether the circle will be highlighted when the tooltip is shown.
Default: true
Name: tooltipsPersistent
Description: 
If you want the tooltips to persist after a click (ie they don't disappear) then you can set this property to true to get this behaviour. Keep in mind that if you have a lot of bars/segments/points/etc then it's possible for the chart to become quite crowded. If you need to subsequently clear all of the tooltips there's an api function available to do that for you and it's called: RGraph.tooltip.persistent.clear() If you want to access any (or all) of the tooltip div tags then you can do so using the RGraph.tooltip.persistent object. This option works when you have the tooltipsEvent property set to mousemove
Default: false
Name: tooltipsNohideonclear
Description: 
Not an option that you'll need particularly often if at all. Setting this to true means that when you call the RGraph.clear api function the tooltip DOES NOT get hidden.
Default: false
Name: tooltipsFormattedPoint
Description: 
When using formatted tooltip strings this is used as the point when using the %{value_formatted} option.
Default: .
Name: tooltipsFormattedThousand
Description: 
When using formatted tooltip strings this is used as the thousand separator when using the %{value_formatted} option.
Default: ,
Name: tooltipsFormattedDecimals
Description: 
When using formatted tooltip strings this specifies the number of decimals when using the %{value_formatted} option.
Default:  0
Name: tooltipsFormattedUnitsPre
Description: 
When using formatted tooltip strings these units are prepended to the number when using the %{value_formatted} option.
Default: (an empty string)
Name: tooltipsFormattedUnitsPost
Description: 
When using formatted tooltip strings these units are appended to the number when using the %{value_formatted} option.
Default: (an empty string)
Name: tooltipsFormattedListType
Description: 
With this property you can switch between an unordered list (the default) and an ordered list. Possible values are ul and ol.
Default: ul
Name: tooltipsFormattedListItems
Description: 
This should be a two-dimensional array of the list items that are to be shown for all of the tooltips. An example of this property is:
tooltipsFormattedListItems: [
    ['Bill','Jerry','Berty'],// First tooltip
    ['Gill','Carrie','Lucy'],// Second tooltip
    ['Pob','Nobby','Hilda']  // Third tooltip
]
You can use CSS to style this list - for example:
.RGraph_tooltip ul#rgraph_formatted_tooltips_list li {
    text-align: left;
    color: yellow;
}
Default: null
Name: tooltipsFormattedTableHeaders
Description: 
When showing a table in the tooltips this can be an array of headers for the table. These are added to the tooltip using th tags.
Default: null
Name: tooltipsFormattedTableData
Description: 
This is the data that is added to the table. This is a 3-dimensional array so it's easy to make a mistake. See the example, copy the code from it and then modify it suit. You'll create fewer bugs this way.
Default: null)
Name: tooltipsPointer
Description: 
By default the tooltips have a small triangular pointer that points to the shape that was clicked on. You can turn this off with this property.
Default: true
Name: tooltipsPointerCss
Description: 
If you want any CSS values applied to the tooltips pointer (a CSS border, for example) then specify an object containing those values to this property. For example:
tooltips: {
    borderLeft: 'gray 2px solid',
    borderBottom: 'gray 2px solid'
}
Default: null
Name: tooltipsPointerOffsetx
Description: 
This allows you to adjust the vertical position of the tooltips pointer.
Default:  0
Name: tooltipsPointerOffsety
Description: 
This allows you to adjust the vertical position of the tooltips pointer (for example, if you add a border you may need to move it down slightly).
Default:  0
Name: tooltipsPositionStatic
Description: 
The new default (as of August 2020) is for tooltips to be positioned statically and not be dependent on the mouse position. If you don't want this for whatever reason, you can disable it with this setting. When you set it to false tooltips are positioned next to the mouse pointer.
Default: true
Name: tooltipsCss
Description: 
If you want to specify some CSS that gets applied to all of the tooltips, but don't want to use the RGraph.tooltips.style object (which gets applied to all of the tooltips on the page for every chart) you can use this property to give some per-object CSS for the tooltips. These are CSS styles that get applied to all of the tooltips for the specific object only. It should look like this:
tooltipsCss: {
    fontFamily: 'Verdana',
    fontSize: '20pt',
}
Default: null
Name: tooltipsOffsetx
Description: 
This property allows you to shift the tooltips left or right.
Default:  0
Name: tooltipsOffsety
Description: 
This property allows you to shift the tooltips up or down.
Default:  0

Miscellaneous properties

Name: highlightStyle
Description: 
By default this is null but you can set it to a function if you wish so that function is called to do the chart highlighting. It's passed the shape object as an argument.
Default: null
Name: highlightStroke
Description: 
This is the color that the circle is highlighted (the stroke) in when the tooltip is shown.
Default: black
Name: highlightFill
Description: 
This is the color that the circle is highlighted in (the fill) when the tooltip is shown.
Default: #fc
Name: linewidth
Description: 
This is the linewidth used to draw the marker.
Default: 2
Name: voffset
Description: 
This allows you to control how "high" the flag is from the bottom of the "flag pole".
Default: 20
Name: events
Description: 
This option is new to version 6.22 and allows you to specify event listener functions for the various RGraph events (eg beforedraw, firstdraw, draw etc). There's an example of its usage in the events section below. It's an object and the properties are the names of the events. The values of those properties can either be the function that you want to attach to the event or an array of functions that you want to run.
Default: {}

Methods

Name: mixed get(string name)
Description: 
This can be used to get properties if necessary. It's normally used after the chart is drawn if you need to get parameters (if you're doing custom coding for example).
Name: object set(string name, mixed value)
Description: 
This can be used to set properties if necessary. It's normally used after the chart is drawn if you need to set additional parameters or change them. The return value is the chart object so you can chain your set calls if you wish.
Name: object on(event name, function listener)
Description: 
This method adds an event listener (such as beforedraw or draw) to the object. It operates similarly to the jquery on function. The first argument is the event that you wish to attach to and the second is the listener function. For example:
obj.on('draw', function (obj)
{
    // Put your code here
});
var obj = new RGraph.Drawing.Marker2({
    id: 'cvs',
    x: x,
    y: y,
    text: 'Note',
}).on('draw', function (obj)
{
    // Put your draw event code here

}).on('click', function (e, shape)
{
    // Handle the click event

}).draw();

You can also use the new (added in version 6.22) events property to add events and that looks like this:

<script>
    new RGraph.Drawing.Marker2({
        id: 'cvs',
        x: x,
        y: y,
        text: 'Note',
        options: {
             events: {
                beforedraw: function () {alert('The beforedraw event fired');},
                draw: [
                    function (obj) {alert('The first draw event listener function.');},
                    function (obj) {alert('The second draw event listener function.');}
                ]
            }
        }
    }).draw();
</script>
Name: object exec(function func)
Description: 
This function can be used to execute a function (immediately). It's not event-based (ie it doesn't run when something happens) - it just runs immediately - and only once. You might use it when you need to get something from the chart when it's drawn and then call the RGraph.redraw function. Because this function only runs once the RGraph.redraw function would not cause a loop - which would happen if you used the draw event.
obj.exec(function (obj)
{
    // Put your code here
});
Name: object getShape(object event)
Description: 
This method makes it easy to get hold of the Marker2 object when it has been clicked on or hovered over. It returns an object which has the following indexes available:
object The Marker2 object.
x The X coordinate for the marker.
y The Y coordinate for the marker.
width The width of the marker.
height The height of the marker.
dataset As there's only ever one element this is always zero.
index As there's only ever one element this is always zero.
sequentialIndex As there's only ever one element this is always zero.
tooltip If a tooltip is associated with the Marker2 object this will be it. id: strings are expanded for you (where the tooltip text is retrieved from the HTML tag with the matching ID).

<script>
    marker2.canvas.onclick = function (e)
    {
        RGraph.redraw();
    
        var canvas = e.target,
            obj    = canvas.__object__,
            shape  = obj.getShape(e);

        if (shape) {            
            // Highlight the main body of the Marker2 object.
            obj.path(
                'lw 10 b r % % % % s black f rgba(255,0,0,0.25)',
                shape.x, shape.y, shape.width, shape.height
            );
        }
    }
</script>

Events

RGraph supports custom events that allow you to easily add interactivity to your charts if required. The following events are available:

Name: beforedraw
Description: 
This event fires at the start of the draw method before anything has been done.
Name: firstdraw
Description: 
This event fires at the end of the draw function - but only the first time that the draw function is called.
Name: draw
Description: 
This event fires at the end of the draw function.
For example:
new RGraph.Drawing.Marker2({
    id:   'cvs',
    x:    200,
    y:    150,
    text: 'Note',
    options: {
        events: {
            draw: function (obj){console.log('The draw event has fired');},
            
            // Alternatively you can give an array of functions
            //to run.
            firstdraw: [
                function (obj) {console.log('First function');},
                function (obj) {console.log('Second function');}
            ]
        }
    }
}).draw();