@ndjson-utils/vega-lite

Create vega-lite spec from JSON or a NDJSON stream

Chart types:

• area
• bar
• line
• multiline
• pie
• scatter

Install

npm install vega-lite @ndjson-utils/vega-lite

Usage

If data.json is a JSON file with an array of objects of this type:

interface Item {
  label: string
  value: number
}

Create a bar chart:

cat data.json | bar | vl2svg > chart.svg

bar creates the vega-lite spec. vl2svg comes from vega-lite and turns a spec into SVG.

bar defaults to keys being called label and value, as in our data. Otherwise, use -l and -v to define the keys (see below).

---

If data.ndjson is a NDJSON file where each line is an object of the type:

interface Item {
  a_key: number
  b_key: number
}

Create a scatterplot:

cat data.ndjson | scatter -x a_key -y b_key -n true | vl2svg > chart.svg

The keys for the x and y axes are defined with -x a_key -y b_key. -n true tells scatter it receives NDJSON.

---

Use --help to see the expected arguments. For example:

pie --help

will return

usage: pie [-h] [-l LABEL] [-v VALUE] [-W WIDTH] [-H HEIGHT] [-n NDJSON]

Create a bar chart from JSON or NDJSON

optional arguments:
  -h, --help            show this help message and exit
  -l LABEL, --label LABEL
                        Label key (defaults to "label")
  -v VALUE, --value VALUE
                        Value key (defaults to "value")
  -W WIDTH, --width WIDTH
                        Chart width (defaults to "400")
  -H HEIGHT, --height HEIGHT
                        Chart height (defaults to "200")
  -n NDJSON, --ndjson NDJSON
                        Takes a NDJSON stream (defaults to JSON)

bar

• -l/--label Label key (defaults to "label")
• -v/--value Value key (defaults to "value")
• -W/--width Chart width (defaults to "400")
• -H/--height Chart height (defaults to "200")
• -n/--ndjson Takes a NDJSON stream (defaults to JSON)

scatter

• -x X axis key (defaults to "x")
• -y Y axis key (defaults to "y")
• -W/--width Chart width (defaults to "400")
• -H/--height Chart height (defaults to "400")
• -n/--ndjson Takes a NDJSON stream (defaults to JSON)

line

Arguments:

• -d/--date Date key (defaults to "date")
• -v/--value Value key (defaults to "value")
• -W/--width Chart width (defaults to "400")
• -H/--height Chart height (defaults to "200")
• -n/--ndjson Takes a NDJSON stream (defaults to JSON)

area

• -d/--date Date key (defaults to "date")
• -v/--value Value key (defaults to "value")
• -W/--width Chart width (defaults to "400")
• -H/--height Chart height (defaults to "200")
• -n/--ndjson Takes a NDJSON stream (defaults to JSON)

multiline

• -d/--date Date key (defaults to "data")
• -v/--values Value keys (comma separated - required)
• -W/--width Chart width (defaults to "400")
• -H/--height Chart height (defaults to "200")
• -n/--ndjson Takes a NDJSON stream (defaults to JSON)

pie

• -l/--label Label key (defaults to "label")
• -v/--value Value key (defaults to "value")
• -W/--width Chart width (defaults to "400")
• -H/--height Chart height (defaults to "200")
• -n/--ndjson Takes a NDJSON stream (defaults to JSON)