Function binnable

packages/sanddance-specs/src/bin.ts:35–139

(prefix: string, domainDataName: string, discreteColumn: DiscreteColumn)

export type Binnable = NativeBinnable | AugmentBinnable;

export function binnable(prefix: string, domainDataName: string, discreteColumn: DiscreteColumn): Binnable {
    const { column, defaultBins, maxbins, maxbinsSignalDisplayName, maxbinsSignalName } = discreteColumn;
    if (column.quantitative) {
        const field = `${prefix}_bin_${exprSafeFieldName(column.name)}`;
        const fieldEnd = `${field}_end`;
        const binSignal = `${field}_bins`;
        const extentSignal = `${field}_bin_extent`;
        domainDataName = `${field}_sequence`;   //override the data name
        const extentTransform: ExtentTransform = {
            type: 'extent',
            field: safeFieldName(column.name),
            signal: extentSignal,
        };
        const maxbinsSignal: Signal = {
            name: maxbinsSignalName,
            value: defaultBins,
            bind: {
                name: maxbinsSignalDisplayName,
                debounce: 50,
                input: 'range',
                min: 1,
                max: maxbins,
                step: 1,
            },
        };
        const binTransform: BinTransform = {
            type: 'bin',
            field: safeFieldName(column.name),
            as: [
                field,
                fieldEnd,
            ],
            signal: binSignal,
            extent: {
                signal: `[${extentSignal}[0], ${extentSignal}[1] + 1e-11]`, //add a tiny bit to the upper extent to force the extra bin - https://github.com/vega/vega/issues/2899
            },
            maxbins: {
                signal: maxbinsSignalName,
            },
        };
        const dataSequence: Data = {
            name: domainDataName,
            transform: [
                {
                    type: 'sequence',
                    start: {
                        signal: `${binSignal}.start`,
                    },
                    stop: {
                        signal: `${binSignal}.stop`,
                    },
                    step: {
                        signal: `${binSignal}.step`,
                    },
                },
                {
                    type: 'formula',
                    expr: 'datum.data',