vega-dataflow

Data Transformation

This feature allows you to apply transformations to data. In this example, a filter transformation is applied to filter out data values less than or equal to 10.

const vega = require('vega-dataflow');
const df = new vega.Dataflow();
const data = df.add([]);
const transform = df.add(vega.transforms.Filter, {expr: 'datum.value > 10', pulse: data});
df.pulse(data, vega.changeset().insert([{value: 5}, {value: 15}])).run();
console.log(transform.value); // [{value: 15}]

Reactive Dataflow

This feature allows you to create reactive dataflow graphs that automatically update when data changes. In this example, an aggregate transformation is used to compute the sum of data values.

const vega = require('vega-dataflow');
const df = new vega.Dataflow();
const data = df.add([]);
const sum = df.add(vega.transforms.Aggregate, {fields: ['value'], ops: ['sum'], pulse: data});
df.pulse(data, vega.changeset().insert([{value: 5}, {value: 15}])).run();
console.log(sum.value); // [{sum_value: 20}]

Parameter Binding

This feature allows you to bind parameters to transformations, making them dynamic and reactive to parameter changes. In this example, a filter transformation is bound to a parameter, and the filter condition updates when the parameter changes.

const vega = require('vega-dataflow');
const df = new vega.Dataflow();
const param = df.add(10);
const data = df.add([]);
const transform = df.add(vega.transforms.Filter, {expr: 'datum.value > param', pulse: data});
df.pulse(data, vega.changeset().insert([{value: 5}, {value: 15}])).run();
console.log(transform.value); // [{value: 15}]
df.update(param, 20).run();
console.log(transform.value); // []