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Handle 0 downloads in growth function #8741

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merged 2 commits into from
May 7, 2025
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Handle 0 downloads in growth function #8741

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30d9800
Handle 0 downloads in growth function
szakarias May 7, 2025
bcb3f72
guard for 0
szakarias May 7, 2025
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4 changes: 4 additions & 0 deletions app/lib/service/download_counts/package_trends.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,10 @@ double computeRelativeGrowthRate(List<int> totalDownloads) {
recentDownloads.reduce((prev, element) => prev + element) /
recentDownloads.length;

if (averageRecentDownloads == 0) {
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@jonasfj jonasfj May 7, 2025

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< 1 might also be worth considering...

Packages with average downloads less than one shouldn't have their growthrate increased..

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@szakarias szakarias May 7, 2025

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I'll keep it in mind but I'll keep it as it is for now. This is the mathematically correct calculation, and hence keeps the abstraction of the function clear. On the caller site we will handle packages with few downloads.

return 0;
}

// We reverse the recentDownloads list for regression, since the first entry
// is the newest point in time. By reversing, we pass the data in
// chronological order.
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8 changes: 7 additions & 1 deletion app/test/service/download_counts/package_trends_test.dart
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Expand Up @@ -11,6 +11,7 @@ void main() {
expect(calculateLinearRegressionSlope([10.0, 20.0, 30.0]), 10.0);
expect(calculateLinearRegressionSlope([30.0, 20.0, 10.0]), -10.0);
expect(calculateLinearRegressionSlope([10.0, 10.0, 10.0]), 0);
expect(calculateLinearRegressionSlope([0.0, 0.0, 0.0]), 0);
});

test('return 0.0 if denominator is very small', () {
Expand All @@ -20,11 +21,16 @@ void main() {
});

group('computeRelativeGrowthRate', () {
test('returns 0.0 for stable downloads meeting threshold', () {
test('returns 0.0 for stable downloads', () {
final downloads = List<int>.generate(analysisWindowDays, (i) => 2000);
expect(computeRelativeGrowthRate(downloads), 0.0);
});

test('returns 0.0 for 0 downloads', () {
final downloads = List<int>.generate(analysisWindowDays, (i) => 0);
expect(computeRelativeGrowthRate(downloads), 0.0);
});

test('calculates positive relative growth rate for positive trend', () {
// Input list (newest first): [1645, 1635, ..., 1355] (30 values)
// Average = 1500 for the first 30 values. Slope: 10.
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