Ordinal series sorting

[bchapuis]

It would be great to add ordinal chart sorting. This could probably be achieved by creating a custom D3 scale based on the ordinal one that use a crossfilter group to manage the order of the absis.

d3.scale.ordinal().domain(["a", "b", "c", "..."]) 

May become:

dc.scale.ordinal().domain(crossfilterGroup)

The main application could be the creation of Pareto Charts.

[NickQiZhu]

Interesting idea. I think you can do that with the existing implementation though probably not as usable. Sort your group in crossfilter then use sorted keys to generate the domain for your x scale. Does that solve your problem?

[bchapuis]

Yes, I have already been able to produce ordered ordinal charts with something like that:

var domain = [];

group.top(Infinity).forEach(function(d) {
    domain[domain.length] = d.key;
});

chart
    .width(900)
    .height(250)
    .dimension(dimension)
    .group(group)
    .x(d3.scale.ordinal().domain(domain))
    .xUnits(dc.units.ordinal);

However, when this chart react to a selection made on another chart, this solution shows its limits. It is not possible to reorganise dynamically the ordinal axis. I wondered if a solution based on d3 scales would allows to handle this use case.

[NickQiZhu]

What if you resets the x domain in .on("filtered", function(chart, filter){...}) hook, will that give you the desired effect?

[bchapuis]

Great, thank you, it seems to be a good start. The bars are well sorted, however the legends remains at the same place. Any idea?

[bchapuis]

It seem's to work when I call the render method that reset the chart completely.

[bchapuis]

Thank you very much, dc.js is a fantastic tool.

It's even possible to use the redraw function to render the chart. The only requirement is to make the x axis elastic and everything works perfectly.

[NickQiZhu]

Glad you have found to way to make it work :-) If you want to force a x axis re-render you can use the following code in postRedraw hook:

chart.renderXAxis(chart.g());