UW Computer Science Professor. Co-Founder of Trifacta. Data, visualization & interaction. @uwdata @trifacta @d3 @vega
Published
Edited
Jan 8, 2021
1 star
dt = aq.table({
i: [1, 2, 3, undefined, 4, 5],
f: Float32Array.from([1.2, 2.3, 3.0, 3.4, null, 4.5]),
n: [4.5, 4.4, 3.4, 3.0, 2.3, 1.2],
b: [true, true, false, true, null, false],
s: ['foo', null, 'bar', 'baz', 'baz', 'bar'],
d: [date(2000,0,1), date(2000,1,2), null, date(2010,6,9), date(2018,0,1), date(2020,10,3)],
u: [null, null, null, null, null, null],
v: arrow.Int8Vector.from([10, 9, 8, 7, 6, 5]),
a: [[1, null, 3], [4, 5], null, [6, 7], [8, 9], []],
l: [[1], [2], [3], [4], [5], [6]],
o: [1, 2, 3, null, 5].map(v => v ? { key: v } : null)
})
at = toArrowTable(dt)
buffer = at.serialize()
[
compareTables(dt, at),
compareTables(dt, arrow.Table.from(buffer)),
compareTables(aq.fromArrow(arrow.Table.from(buffer)), at)
]
function toArrowTable(table, types = {}) {
const names = table.columnNames();
const vectors = names.map(name => toArrowVector(table, name, types[name]));
return arrow.Table.new(vectors, names);
}
function toArrowVector(table, name, type) {
const column = table.column(name);
const reify = table.isFiltered() || table.isOrdered();
if (!type) {
if (!reify && (column instanceof arrow.Column || column instanceof arrow.Vector)) {
return column;
}
if (isTypedArray(column.data)) {
type = typeMap.get(column.data.constructor.name);
}
}
type = type || inferType(profile(table, name));
const vectorType = getVectorType(type);
// TODO: handle missing type / failed inference
if (!vectorType) return null;
return arrow.Vector.from({ type: vectorType, values: iterator(table, name) });
}
Purpose-built for displays of data
Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
