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README.md

vlbuildr

The goal of vlbuildr is to provide an R api for building up vega-lite specs.

Current status

This package is in early stages at the moment. Most of a “v0” of the public facing API has been built (although definitely not locked-down yet!).

However, the internals of the package might change substantially to provide greater robustness, make it harder to make invalid specs, and/or provide more info when making invalid spec. The current approach seeks to make it easy to build up specs, provided your input arguments are okay… but it does no checking of those inputs and you can very easily make invalid specs! Still TBD exactly how rigorous/helpful this package will aim to be with regards to bad specifications..

The documentation is also still very bare-bones. The parameter documentation for functions is fairly complete, however, as it relies on descriptions pulled directly from the Vega-Lite schema.

Inspiration and related work

The API for this package is heavily inspired by the vegalite R package, but is rebuilt from scratch to (1) build up the API semi-automatically based on the Vega-lite schema (an approach inspired by Altair and vega-lite-api) and (2) take advantage of the htmlwidget infrastucture for vega specs provided by the vegawidget package.

Building

Much of the public API is auto-generated via the build.R script in the inst directory. The script makes uses of another package, vlmetabuildr.

Examples

These are some examples showing current capabilities; see pkgdown site for more examples, including interactive ones.

library(vlbuildr)
library(vegawidget)
vl_chart() %>%
   vl_add_data(values = mtcars) %>%
   vl_mark_point() %>%
   vl_encode_x("wt") %>%
   vl_encode_y("mpg") 

vl_chart() %>%
  vl_add_data(url = "https://vega.github.io/vega-editor/app/data/population.json") %>%
  vl_calculate(calculate = "datum.sex == 2 ? 'Female' : 'Male'", 
               as = "gender") %>%
  vl_filter("datum.year == 2000") %>%
  vl_encode(x = "age:O", y = "people:Q", color = "gender:N") %>%
  vl_scale_x(rangeStep = 17) %>%
  vl_stack_y("normalize") %>%
  vl_aggregate_y("sum") %>%
  vl_axis_y(title = "population") %>%
  vl_mark_bar() 

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