Straight line Dojo graphs with no axis

When Swivel graphs a set of data, it shows a sparkline graph in addition to the big graph. A sparkline graph is the small version of the graph with no axis. Dojo charts provides this capability.

But, we ran into a problem. When we tried graphing straight lines (lines with equal Y values) the sparkline didn't show up. We kept thinking that dojo was drawing a straight line down below the drawing area. That wasn't the case. It turned out that when dojo draws with no axes it uses this little formula in dojotoolkit/dojox/charting/scaler/primitive.js

    buildScaler: function(/*Number*/ min, /*Number*/ max, /*Number*/ span, /*Object*/ kwArgs){
        return {
            bounds: {
                lower: min,
                upper: max,
                from:  min,
                to:    max,
                scale:  span/(max - min),
                span:  span
            },
            scaler: dojox.charting.scaler.primitive
        };
    },

So if you pay a close attention to this line: scale: span/(max -min), in a straight line all the y values are equal so max becomes equal to min so the (max - min) equation becomes zero making span/ (max -min) going to infinity and makes scale be a NaN value in javascript.

This is simply fixed by three lines of code:

if (min == max) {
  scale = 1;
  min = -1;
} else {
  scale = span/(max - min);
}

That's it. min = -1 makes the drawing of the line to go up 1 pixel. If you don't add that line, your graph would not show up in IE.