What kind of plots can you make with this? This has real potential in the big-data and scientific fields. Plotting is hard and if you can easily tie together many data sources and models that are popular onto time series and geospatial plots this will be a winning combo go scientists.
The real interest is in manipulating the data, not just plotting it. Actually after manipulating, if you need to produce a plot the tools you mention can be used.
Most of the time. Unless you want or need a bespoke visualization, Plot will let you construct a meaningful plot with much less time and effort. (That said, Plot is brand new and still under development, so it might not yet have the specific features you need.)
Don't forget text plotting, that's the hard part. The technical challenge is not huge, but the amount of small and "easy" features a good plotting lib needs is huge.
The biggest issue I had with plot libraries is that they don't work out of the box for millions of data points. Last time I was doing a data science project, I tried all of the major plotting libraries and none of them works well beyond a few million data points. I want a graph that I can visualize and zoom in/out in real-time and that became the hard part of the project. Only one product claims to be able to handle it using GPUs in the cloud and it needs a paid subscription and uploading your data into the cloud. I don't want yet another library, but some library that works really well and can utilize local GPU for plotting.
When I was in the business of making plots, ggplot2 was by far my favourite. It seemed odd at first, but eventually it clicked and it felt great. Once you grok the grammar of graphics you'll find you can really quickly express all kinds of plots from any given dataset. I would routinely impress people with how quickly I could visualise data.
I use it mostly for exploratory data analysis. I'm pretty quick with making plots in it (I've used it since v1.2), so I tend to use it for reading in a data set, and them playing around with it. It can handle datasets in the hundreds of thousands of points (still in memory) pretty quickly. You can plot 200k points a series without it slowing down.
On those rare occasions I need to solve equations or do some calculus, there's nothing better.
I'm not usually a fan of plotting tools. I prefer instead to make custom plots in D3. Usually plotting tools are too simplistic to be useful for significantly valuable use cases. This however is an example of a "simple" plotting tool bringing lots of value. Kudos. This is great.
This is exactly why I still use R. Throw data in a file, suck it into R, start playing with slicing and visualization with a few commands. Once I get something interesting, a few more tweaks and I have a nice, descriptive graph.
For me the most useful features of Plot over other libraries are the declarative transforms: bin, stack, map, filter, etc. This means that a lot of the data munging that you would normally do before passing things off to the plotting library are done by Plot itself. Why would you want that? Well these transforms are now "facet aware" - if you want to facet on some some qualitative property, slap a `fx: property` on your mark and your transforms will then be run for each subplot.
Secondly, I simply find the API to be very tastefully built. The Geo API (https://observablehq.com/plot/marks/geo) is a particular highlight. I've used Plot for about 1.5 years for recreational side projects - it has genuinely kept me entertained for many hours in no small part due to its interface design.
Ggplot is extremely powerful if you can grok its grammar, which takes some getting used to. But I'd assume that if you see a graph in a scientific paper it's made with ggplot.
Having many data points you want to explore you are always going to be at the edges of what your hardware and software can produce.
The last really big datasets I worked with were for my thesis and I had to do subsampling to below 10% to get results within 10minutes or so and that was basically plotting midi recordings of piano performances, so nothing gigantic
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