Line / Marker Showing Updates During the Life of the Data Set

[jchapin]

Related to: #9.

We want to show through the timeline for left to right major markers in the life of the data set... updates.

Data Set:  |===|=====|=====|=====|=====|=====|=====|     |

1. Each pipe in the above diagram signifies when an update was made to a data set.
2. This may be possible with the JavaScript library used to render the timeline, or we may have to roll our own solution.
3. We may have to extend / create a new model related to data sets in order to get historical information logged on when updates take place.

[mshenfield]

Google Charts Support

Looking through the Google Charts documentation it doesn't look like there's an easy way to do this. Some other chart types support an "annotation" role that creates exactly what you described, a vertical line with optional text, but it is not available in the timeline. Google Charts isn't open source and the only issue that came close to addressing this is a low-priority enhancement filed 6 months ago. This also effects issue #9.

Alternatives

Not sure what the next step is - I wanted to add links back to the data portal in #16, which isn't possible with ChartKick according to an open issue. HighChart's canned options for a timeline seem weak, so I don't see that as an alternative. I think I have a good enough handle on Google Charts I can replace ChartKick with a GoogleCharts script. But that still wouldn't give us the line marker.

There is an open source d3 plugin for timelines that ends up looking something like this:

It seems a little immature but I think we could modify it enough to add an "annotation" when updates occured. It also isn't responsive - we'd have to hand code that in using something like this.

Data Issue

There is also a separate issue grabbing a history of modification dates from the Socrata API. I've posted the question on Stack Overflow, but in short the documented metadata endpoint and the data.json endpoint we pull from now only return the most recent date of modification. I don't think there's a good way around this beyond sending an issue to Socrata. I've opened up a new issue (#18) to address it here.