Transformations

Data transforms are defined with msc.transform(...) and applied with scene.derive(...):

let scene = msc.scene();
let table = await msc.csv("data.csv");
let spec = msc.transform("filter", { attribute: "year", type: "interval", value: [1955, 1955] });
let filtered = scene.derive(table, spec);

scene.derive(...) always returns a new DataTable.

Binning#

The binning transformation assigns each input row to a numeric interval. This is used in visualizations such as histograms (example demos: histogram, dynamic binning).

let binSpec = msc.transform("bin", { attribute: "weight(lbs)", numBins: 8 });
let binned = scene.derive(table, binSpec);

The binning transformation exposes generated attribute names you can use in encodings:

• binSpec.binIdAttr: bin id attribute (for grouping/repeat)
• binSpec.startAttr: bin start value
• binSpec.endAttr: bin end value
• binSpec.actualNumBins: final number of bins after boundary adjustment

Filtering#

The filtering transformation keeps only rows that satisfy a predicate spec. Example demos: tower chart and DimpVis

let yearFilter = msc.transform("filter", {
    attribute: "year",
    type: "interval",
    value: [1955, 1955]
});
let yearData = scene.derive(table, yearFilter);

Kernel Density Estimation#

The KDE transformation estimates a density curve for a numeric attribute. Example demos: density plot and ridgeline plot.

let density = scene.derive(table, msc.transform("kde", {
    attribute: "weight(lbs)",
    newAttribute: "weight_density",
    min: 1500,
    max: 5000,
    interval: 100,
    bandwidth: 10
}));

Custom transform#

The custom transformation lets you define transform logic directly. Example demos: histograms cross filtering and index chart. The callback receives the input table, output table, and mutable spec object:

let tableSpec = msc.transform("custom", (inTbl, outTbl, spec) => {
    let rows = spec.selectedRows ? spec.selectedRows.slice(0, 25) : inTbl.rows().slice(0, 25);
    outTbl.load(rows);
}, { selectedRows: null });

let derived = scene.derive(table, tableSpec);