Dygraphs vertical line with label

Question

I need to place a vertical line with a label on my dygraph like the National holiday line in this example - http://www.fusioncharts.com/dev/chart-attributes.html?chart=msline

I have searched google for about 2 hours and can't find any examples. Can someone shoot me an example or put me on the right track? Thanks.

Answer 1

Best practice today is to add highlighted region using underlay callback ( example ).

try specifying the "underlayCallback" option within your "new Dygraph()" call. Use HTML Canvas context to draw the line.

On creating your graph:

// Graph range on X axis:
var xMin=0, xMax=1;
// horizontal line Y value:
var yValue = 0.5;

new Dygraph(document.getElementById('garph'), data, {
    // Graph options
    underlayCallback: function(ctx, area, dygraph) {
        var xLeft =  dygraph.toDomCoords(Min, yValue);
        var xRight = dygraph.toDomCoords(Max, yValue);
        ctx.strokeStyle = 'black';
        ctx.beginPath();
        ctx.moveTo(xLeft[0],  xLeft[1] );
        ctx.lineTo(xRight[0], xRight[1]);
        ctx.closePath();
        ctx.stroke();
    }
});

Note this is a very general example, as you haven't shown your own code.