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Posted to issues@flink.apache.org by "Fanoid (via GitHub)" <gi...@apache.org> on 2023/03/21 03:05:11 UTC
[GitHub] [flink-ml] Fanoid commented on a diff in pull request #222: [FLINK-31029] Fix bug when using quantile in KbinsDiscretizer
Fanoid commented on code in PR #222:
URL: https://github.com/apache/flink-ml/pull/222#discussion_r1142849665
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flink-ml-lib/src/main/java/org/apache/flink/ml/feature/kbinsdiscretizer/KBinsDiscretizer.java:
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@@ -220,22 +220,46 @@ private static double[][] findBinEdgesWithQuantileStrategy(
binEdges[columnId] =
new double[] {Double.NEGATIVE_INFINITY, Double.POSITIVE_INFINITY};
} else {
- double width = 1.0 * features.length / numBins;
- double[] tempBinEdges = new double[numBins + 1];
+ double[] tempBinEdges;
+ if (features.length > numBins) {
+ double width = 1.0 * features.length / numBins;
+ tempBinEdges = new double[numBins + 1];
- for (int binEdgeId = 0; binEdgeId < numBins; binEdgeId++) {
- tempBinEdges[binEdgeId] = features[(int) (binEdgeId * width)];
+ for (int binEdgeId = 0; binEdgeId < numBins; binEdgeId++) {
+ tempBinEdges[binEdgeId] = features[(int) (binEdgeId * width)];
+ }
+ tempBinEdges[numBins] = features[numData - 1];
+ } else {
+ tempBinEdges = features;
}
- tempBinEdges[numBins] = features[numData - 1];
- // Removes bins that are empty, i.e., the left edge equals to the right edge.
- Set<Double> edges = new HashSet<>(numBins);
+ // Bins with zero width should be converted to a non-empty bin.
+ Map<Double, Integer> edgesAndCnt = new HashMap<>(numBins);
for (double edge : tempBinEdges) {
+ edgesAndCnt.put(edge, edgesAndCnt.getOrDefault(edge, 0) + 1);
+ }
+ List<Double> edges = new ArrayList<>();
+ for (Map.Entry<Double, Integer> edgeAndCnt : edgesAndCnt.entrySet()) {
+ double edge = edgeAndCnt.getKey();
+ int cnt = edgeAndCnt.getValue();
edges.add(edge);
+ if (cnt > 1) {
+ edges.add(edge);
+ }
+ }
+ tempBinEdges = edges.stream().mapToDouble(Double::doubleValue).toArray();
+ Arrays.sort(tempBinEdges);
+ int i = 1;
+ for (; i < tempBinEdges.length - 1; i++) {
+ if (tempBinEdges[i] == tempBinEdges[i - 1]) {
+ tempBinEdges[i] = (tempBinEdges[i + 1] + tempBinEdges[i - 1]) / 2;
+ }
+ }
+ if (tempBinEdges[i] == tempBinEdges[i - 1]) {
+ binEdges[columnId] = Arrays.copyOfRange(tempBinEdges, 0, i);
Review Comment:
Does this line means the last bin edge is dropped?
If so, when the `tempBinEdges ` are `[0, 1, 1]`, `binEdges ` will be `[0, 1]`. Then all values are in same bin in `KBinsDiscretizerModel#transform`.
It seems this case should be handle separately when there are only two distinct bin edges.
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