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- import { FeatureCollection, Point } from 'geojson';
- interface QuadratAnalysisResult {
- criticalValue: number;
- maxAbsoluteDifference: number;
- isRandom: boolean;
- observedDistribution: number[];
- }
- /**
- * Quadrat analysis lays a set of equal-size areas(quadrat) over the study area and counts
- * the number of features in each quadrat and creates a frequency table.
- * The table lists the number of quadrats containing no features,
- * the number containing one feature, two features, and so on,
- * all the way up to the quadrat containing the most features.
- * The method then creates the frequency table for the random distribution, usually based on a Poisson distribution.
- * The method uses the distribution to calculate the probability for 0 feature occuring,
- * 1 feature occuring, 2 features, and so on,
- * and lists these probabilities in the frequency table.
- * By comparing the two frequency tables, you can see whether the features create a pattern.
- * If the table for the observed distribution has more quadrats containing many features than the
- * table for the random distribution dose, then the features create a clustered pattern.
- *
- * It is hard to judge the frequency tables are similar or different just by looking at them.
- * So, we can use serval statistical tests to find out how much the frequency tables differ.
- * We use Kolmogorov-Smirnov test.This method calculates cumulative probabilities for both distributions,
- * and then compares the cumulative probabilities at each class level and selects the largest absolute difference D.
- * Then, the test compares D to the critical value for a confidence level you specify.
- * If D is greater than the critical value, the difference between the observed distribution and
- * the random distribution is significant. The greater the value the bigger the difference.
- *
- * Traditionally, squares are used for the shape of the quadrats, in a regular grid(square-grid).
- * Some researchers suggest that the quadrat size equal twice the size of mean area per feature,
- * which is simply the area of the study area divided by the number of features.
- *
- *
- * @function
- * @param {FeatureCollection<Point>} pointFeatureSet point set to study
- * @param {Object} [options={}] optional parameters
- * @param {[number, number, number, number]} [options.studyBbox] bbox representing the study area
- * @param {20 | 15 | 10 | 5 | 2 | 1} [options.confidenceLevel=20] a confidence level.
- * The unit is percentage . 5 means 95%, value must be in {@link K_TABLE}
- * @returns {QuadratAnalysisResult} result
- * @example
- *
- * var bbox = [-65, 40, -63, 42];
- * var dataset = turf.randomPoint(100, { bbox: bbox });
- * var result = turf.quadratAnalysis(dataset);
- *
- */
- declare function quadratAnalysis(pointFeatureSet: FeatureCollection<Point>, options: {
- studyBbox?: [number, number, number, number];
- confidenceLevel?: 20 | 15 | 10 | 5 | 2 | 1;
- }): QuadratAnalysisResult;
- export { type QuadratAnalysisResult, quadratAnalysis as default, quadratAnalysis };
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