@uwdata/mosaic-sql/dist/src/transforms/line-density.d.ts

SQL query construction and analysis.

import type { ExprValue } from '../types.js';
import { type SelectQuery } from '../ast/query.js';
/**
 * Compute line segment densities over a gridded 2D domain. The returned
 * query uses multiple subqueries (CTEs) to identify line segment end point
 * pairs, perform line rasterization in-database, normalize arc lengths,
 * and then sum results for all line series to produce a density map.
 * Based on Moritz and Fisher's work: https://arxiv.org/abs/1808.06019
 * @param q The base query over the data.
 * @param x Bin expression for x dimension.
 *  Provides gridded x coordinates, potentially with a fractional component.
 * @param y Bin expression for x dimension.
 *  Provides gridded y coordinates, potentially with a fractional component.
 * @param z Group by columns that segment data into individual line
 *  series. An empty array indicates there is only a single line series.
 * @param xn The number of grid bins for the x dimension.
 * @param yn The number of grid bins for the y dimension.
 * @param groupby Additional group by expressions. Separate
 *  line density maps are created for each of these groups.
 * @param normalize Flag toggling approximate arc-length normalization to
 *  improve accuracy and reduce artifacts (default `true`).
 */
export declare function lineDensity(q: SelectQuery, x: ExprValue, y: ExprValue, z: string[], xn: number, yn: number, groupby?: string[], normalize?: boolean): SelectQuery;
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