[ngould]

I like Altair, and have built a couple analyses and products with it. In general, it's a convenient way to do exploratory data analysis. But I have found it to be sort of inflexible for simple variations on common chart types -- especially if you want to augment a chart with information that is not in the dataframe instance used to instantiate the altair.Chart object. For instance, if you want to draw a line overlay on a chart, the best way to do it (to my knowledge) is append the start and end coordinates to your dataframe before calling mark_line().

I'm curious whether anyone else has had similar frustrations? I wonder what enhancements might make practical use of Altair for those use cases easier.

[kanitw]

For drawing lines with specific coordinate values, you can just encode position (x, y, x2, y2) of lines or rules with constant values?

If you have specific use case that's really cumbersome in Altair/Vega-Lite, please feel free to file an issue. We're happy to help improve the tool. :)

Disclosure: I'm a co-author of Vega-Lite.