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mindok / contex

Charting and graphing library for Elixir
https://contex-charts.org/
MIT License
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TimeSeries BarChart? #41

Open chasers opened 3 years ago

chasers commented 3 years ago

It looks like there is not a way to use the TimeSeries scale with a bar chart?

I like to use time series bar charts for things a lot. Would love to be able to do this Contex. I can try to implement if you're up for it?

mindok commented 3 years ago

Hi @chasers, Yes - that's correct. Currently the bar chart is set up to use an "Ordinal Scale" only. This has a couple of special features to control plotting of bars - it has a get_band function that calculates the required width of a bar on the chart in plotting coordinates based on the required padding in plotting coordinates.

Ordinal Scale doesn't care about the data type, so you could easily create a dataset, sorted by date (and with pre-formatted date labels to make life easier) and feed that into the barchart. You would have to ensure regular time periods (e.g. daily) and create a row in the dataset for missing time periods with a zero value.

In terms of implementing a time series scale for a barchart, feel free. I'm happy to accept PRs. It may be worth getting your thoughts on use cases first and we could discuss possible approaches. There are a couple of potential approaches depending on what you are trying to achieve.

chasers commented 3 years ago

Thanks!

Yeah I've got it mostly there. This is now on our billing page:

Screen Shot 2021-01-12 at 3 44 18 PM

I tried unsuccessfully to overwrite the x-axis with my own. It's just the labels get a little noisy with more than 30 days of data.

Can I simply customize the number of ticks in the x-axis? Like put a tick at every Nth column?

I'm evaluating this for more generalized simple dashboarding. So far I haven't run into any blockers really. LinePlot will be great!

mindok commented 3 years ago

Hi @chasers, looks good!

No - there isn't an option to label every Nth for the ordinal scale as yet. It wouldn't be hard to do at all. Or we could set a max_category_labels or similar on the BarChart and pass it through to the scale and have the scale calculate how many to skip. That would be pretty quick & simple to do.

srowley commented 3 years ago

It occurs to me that a simple (if sort of indirect) way to support this would be to add separate classes to the x and y-axis ticks and labels, and then let the user set the stroke/fill to none (or whatever) with :nth-of-type selectors. That would have no impact on the API (or existing style sheets) with the added benefit of allowing some more granular styling generally.