kaknikhil commented on a change in pull request #441: Kmeans: simplified
silhouette per point for k-means
URL: https://github.com/apache/madlib/pull/441#discussion_r325328731
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File path: src/ports/postgres/modules/kmeans/test/kmeans.sql_in
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@@ -81,11 +81,37 @@ COPY km_sample (pid, points) FROM stdin DELIMITER '|';
10 | {13.86, 1.35, 2.27, 16, 98, 2.98, 3.15, 0.22, 1.8500, 7.2199, 1.01, NULL,
1045}
\.
+DROP TABLE IF EXISTS centroids_null, silh_out;
+CREATE TABLE centroids_null AS
SELECT * FROM kmeanspp('km_sample', 'points', 2,
'MADLIB_SCHEMA.squared_dist_norm2',
'MADLIB_SCHEMA.avg', 20, 0.001);
+SELECT simple_silhouette_points('km_sample', 'silh_out', 'pid', 'points',
+ 'centroids_null', 'centroids',
+ 'MADLIB_SCHEMA.squared_dist_norm2');
+
+SELECT assert(silh > 0, 'Incorrect silhouette value')
+FROM silh_out
+WHERE silh IS NOT NULL;
+
+DROP TABLE IF EXISTS silh_out;
+SELECT simple_silhouette_points('km_sample', 'silh_out', 'pid', 'points',
+ 'centroids_null', 'centroids');
+
+SELECT assert(count(*) = 9, 'Incorrect silhouette count')
Review comment:
1. Since the silhouette calculation is deterministic, if we create our own
centroids table , can't we assert the actual values for all the 9 points ?
* If we do this, then we might also be able to add a test for the case
when distances[2] == 0, what do you think ?
1. We can add a few more asserts here
* `pid` values should be the same as the source table
* `centroid_id` and `neighbor_centroid_id` should have different values
for each pid
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