https://github.com/rwpenney/vl4s
Tool for auto-generating a Scala plotting library from Vega-Lite schema, to support interactive web-based graphs and visualizations.
https://github.com/rwpenney/vl4s
data-science data-visualization json-schema plot plotting scala vega-lite
Last synced: 17 days ago
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Tool for auto-generating a Scala plotting library from Vega-Lite schema, to support interactive web-based graphs and visualizations.
- Host: GitHub
- URL: https://github.com/rwpenney/vl4s
- Owner: rwpenney
- License: mpl-2.0
- Created: 2017-11-19T18:52:42.000Z (about 8 years ago)
- Default Branch: master
- Last Pushed: 2018-06-04T15:47:09.000Z (over 7 years ago)
- Last Synced: 2026-01-12T21:48:03.610Z (21 days ago)
- Topics: data-science, data-visualization, json-schema, plot, plotting, scala, vega-lite
- Language: Scala
- Homepage:
- Size: 147 KB
- Stars: 2
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
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README
# VL4S (Vega-Lite for Scala)
vl4s is a tool for automatically generating
a [Scala](https://www.scala-lang.org) library
via which interactive plots can be generated conforming
to the [Vega-Lite](https://vega.github.io/vega-lite) specification.
vl4s is intended to allow the
JSON [schema](https://github.com/vega/schema/tree/master/vega-lite)
provided by Vega-Lite to be converted into a Scala API
which provides natural, and type-safe,
ways of describing plots in Scala and emitting Vega-Lite JSON documents
that can be embedded in web-pages.
This is an alternative approach to that of [Vegas](https://www.vegas-viz.org/),
and [Argus](https://github.com/aishfenton/Argus), aiming to create
a DSL that is closer to the structure of the underlying JSON schema
(hence, hopefully, easier to document) and allowing export
of a [json4s](http://json4s.org) datastructure that could
be customized by the user.
The build-system is managed by [SBT](http://www.scala-sbt.org/),
and consists of two projects:
* the "root" project, which must be compiled and run to generate
the file "vl4s/src/main/scala/auto-vega.scala"
from either the upstream VegaLite schema based on a version-number
supplied with the "-V" command-line argument,
or a local copy of a schema file (e.g. "v2.1.3.json")
* the "vl4s" project, which will build the VegaLite API itself,
and allows creation of VegaLite JSON documents from
a user-supplied plot specification.
The tool supports the entire Vega-Lite 2.4 grammar,
including generation of interactive line plots,
and histograms with aggregation operations, repeats, selections, etc.
## Example
Given a tab-separated datafile representing the sizes of packages
in a [Debian](https://www.debian.org) system,
one can generate an interactive Vega-Lite plot
using a recipe such as:
```scala
import org.json4s._
import org.json4s.native.JsonMethods.{ pretty, render }
import uk.rwpenney.vl4s._
import uk.rwpenney.vl4s.ShortcutImplicits._
val spec = SimpleSpec() .
data("apt-package-sizes.tsv") .
selection(
Map("chosen" -> SingleSelection() .
encodings(Seq(SingleDefChannel.color)) .
vtype(SingleSelection_type.single))) .
mark(Mark.bar) .
encoding(EncodingWithFacet() .
>> { enc => enc .
x(enc.XYaxisDef .
axis(Axis() .
title("log(size)")) .
field("logSize") .
vtype(BasicType.quantitative) .
bin(BinParams() .
maxbins(20))) .
y(enc.XYaxisDef .
axis(Axis() .
title("count")) .
field("*") .
vtype(BasicType.quantitative) .
aggregate(AggregateOp.count)) .
color(MarkPropValueDefWithCondition() .
condition(ConditionalSelection_MarkPropFieldDef_() .
field("simpleSection") .
selection("chosen") .
vtype(BasicType.nominal)) .
value("grey"))
}
)
val json = spec.toJValue
println(pretty(render(json)))
```
This will generate a JSON document of the following form:
```json
{
"data":{
"url":"apt-package-sizes.tsv"
},
"selection":{
"chosen":{
"encodings":["color"],
"type":"single"
}
},
"mark":"bar",
"encoding":{
"x":{
"axis":{
"title":"log(size)"
},
"field":"logSize",
"type":"quantitative",
"bin":{
"maxbins":20.0
}
},
"y":{
"axis":{
"title":"count"
},
"field":"*",
"type":"quantitative",
"aggregate":"count"
},
"color":{
"condition":{
"field":"simpleSection",
"selection":"chosen",
"type":"nominal"
},
"value":"grey"
}
}
}
```
Alternatively, one can use the methods in the ExportImplicits object
to wrap this in an HTML `
` for inclusion in a web-page.
There are more [examples](vl4s-demo/src/main/scala/main.scala)
beneath the [vl4s-demo](vl4s-demo/src/main/scala) source directory.