jquery.flot.threshold.js

/*
Flot plugin for thresholding data. Controlled through the option
"threshold" in either the global series options

  series: {
    threshold: {
      below: number
      color: colorspec
    }
  }

or in a specific series

  $.plot($("#placeholder"), [{ data: [ ... ], threshold: { ... }}])
  
An array can be passed for multiple thresholding

  threshold: [{
    below: number1
    color: color1
  },{
    below: number2
    color: color2
  }]

These multiple threshold objects can be passed in any order since they
are sorted by the processing function.

The data points below "below" are drawn with the specified color. This
makes it easy to mark points below 0, e.g. for budget data.

Internally, the plugin works by splitting the data into two series,
above and below the threshold. The extra series below the threshold
will have its label cleared and the special "originSeries" attribute
set to the original series. You may need to check for this in hover
events.
*/

(function ($) {
    var options = {
        series: { threshold: null } // or { below: number, color: color spec}
    };
    
    function init(plot) {
        function thresholdData(plot, s, datapoints, below, color) {
            var ps = datapoints.pointsize, i, x, y, p, prevp,
                thresholded = $.extend({}, s); // note: shallow copy

            thresholded.datapoints = { points: [], pointsize: ps, format: datapoints.format };
            thresholded.label = null;
            thresholded.color = color;
            thresholded.threshold = null;
            thresholded.originSeries = s;
            thresholded.data = [];
 
            var origpoints = datapoints.points,
                addCrossingPoints = s.lines.show;

            threspoints = [];
            newpoints = [];

            for (i = 0; i < origpoints.length; i += ps) {
                x = origpoints[i]
                y = origpoints[i + 1];

                prevp = p;
                if (y < below)
                    p = threspoints;
                else
                    p = newpoints;

                if (addCrossingPoints && prevp != p && x != null
                    && i > 0 && origpoints[i - ps] != null) {
                    var interx = (x - origpoints[i - ps]) / (y - origpoints[i - ps + 1]) * (below - y) + x;
                    prevp.push(interx);
                    prevp.push(below);
                    for (m = 2; m < ps; ++m)
                        prevp.push(origpoints[i + m]);
                    
                    p.push(null); // start new segment
                    p.push(null);
                    for (m = 2; m < ps; ++m)
                        p.push(origpoints[i + m]);
                    p.push(interx);
                    p.push(below);
                    for (m = 2; m < ps; ++m)
                        p.push(origpoints[i + m]);
                }

                p.push(x);
                p.push(y);
                for (m = 2; m < ps; ++m)
                    p.push(origpoints[i + m]);
            }

            datapoints.points = newpoints;
            thresholded.datapoints.points = threspoints;
            
            if (thresholded.datapoints.points.length > 0)
                plot.getData().push(thresholded);
                
            // FIXME: there are probably some edge cases left in bars
        }
        
        function processThresholds(plot, s, datapoints) {
            if (!s.threshold)
                return;
            
            if (s.threshold instanceof Array) {
                s.threshold.sort(function(a, b) {
                    return a.below - b.below;
                });
                
                $(s.threshold).each(function(i, th) {
                    thresholdData(plot, s, datapoints, th.below, th.color);
                });
            }
            else {
                thresholdData(plot, s, datapoints, s.threshold.below, s.threshold.color);
            }
        }
        
        plot.hooks.processDatapoints.push(processThresholds);
    }
    
    $.plot.plugins.push({
        init: init,
        options: options,
        name: 'threshold',
        version: '1.2'
    });
})(jQuery);