I am trying to work with an already reactive library (Vega) in Observable. My current progress is at https://beta.observablehq.com/@domoritz/rotating-earth . Vega has “signals” as reactive variables. In my example, I am trying to set the signal value to the reactive rotation value. The problem is tha…

I’m no Vega expert, but it looks like in your current sketch, Vega waits for you to mouse back over the globe before updating with the new rotation position. I find that if I change: view.signal('rotation', rotation) to { view.signal('rotation', rotation); view.run(); } … it updates as one …

Well, looks like you know Vega better than I do :wink: view.signal('rotation', rotation).run() is a shortcut for what you wrote. I am still trying to understand the dependency graph on Observable. Why don’t all cells that depend on the view get re-evaluated when the rotation changes? I would expect…

Here is a little experiment: https://beta.observablehq.com/@domoritz/dependency-experiment . Note how a.foo is 42 and the text says so as well. When I uncomment the last cell and run it, the content of a changes but the text does not update automatically. However, when I rerun the text cell, the tex…

Yep. The model may be a little bit simpler than what you’re imagining. It wraps a functional programming skin around JavaScript, so that each cell in Observable acts as a function body — whatever is returned by the cell becomes the cell’s value, and whenever that value changes (actually changes it…

Thanks for the explanation. It’s great for Vega that you are not tracking changes to objects as it allows us to use the reactivity of Vega. I’m excited to play more with Observable!

To elaborate on Jeremy’s comment, I would say as a rule of thumb: prefer immutability, and opt-in to mutability when necessary for performance. Mutation adds complexity because now you have to worry about managing mutable state yourself, rather than relying on automatic reactivity, but gives you mor…

Can you explain the error I showed in the GIF above? What’s the initialization strategy of a notebook?

Sure. Your dependency graph looks like this: [image] The directed edges here indicate references: for example, vegaSpec references vl, so Observable won’t evaluate the vegaSpec cell until vl resolves (which involves requiring vega-lite@2 from unpkg). The important thing missing from this graph i…

Thanks! It was super useful to see these dependency graphs.

Cut dependency graph

mbostock February 1, 2018, 9:00pm 11

Hopefully the dependency graphs will be built-in at some point in the near future!

Slider Changes Re-Creating WebGL Context?

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Cut dependency graph

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