From e2ef106ffc68f7b9ae9f6d23d8008e62f7032365 Mon Sep 17 00:00:00 2001
From: Marcel Gerber <mgerber59@gmail.com>
Date: Thu, 15 Aug 2024 12:12:07 +0100
Subject: [PATCH] enhance: with `MissingDataStrategy.auto`, drop entities with
 single non-error data point

---
 .../core-table/src/OwidTable.ts               | 14 ++++++++++
 .../stackedCharts/StackedDiscreteBarChart.tsx | 27 +++++++++++++------
 2 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/packages/@ourworldindata/core-table/src/OwidTable.ts b/packages/@ourworldindata/core-table/src/OwidTable.ts
index fda142017bc..93e5a050130 100644
--- a/packages/@ourworldindata/core-table/src/OwidTable.ts
+++ b/packages/@ourworldindata/core-table/src/OwidTable.ts
@@ -277,6 +277,20 @@ export class OwidTable extends CoreTable<OwidRow, OwidColumnDef> {
         )
     }
 
+    dropRowsWithAtLeastThisManyErrorValuesForColumns(
+        slugs: ColumnSlug[],
+        minErrorValues: number
+    ): this {
+        return this.rowFilter(
+            (row) =>
+                slugs.filter((slug) => !isNotErrorValue(row[slug])).length >=
+                minErrorValues,
+            `Drop rows with at least ${minErrorValues} ErrorValues in every column: ${slugs.join(
+                ", "
+            )}`
+        )
+    }
+
     // Drop _all rows_ for an entity if there is any column that has no valid values for that entity.
     dropEntitiesThatHaveNoDataInSomeColumn(columnSlugs: ColumnSlug[]): this {
         const indexesByEntityName = this.rowIndicesByEntityName
diff --git a/packages/@ourworldindata/grapher/src/stackedCharts/StackedDiscreteBarChart.tsx b/packages/@ourworldindata/grapher/src/stackedCharts/StackedDiscreteBarChart.tsx
index f6fd375ec56..b1acb46152e 100644
--- a/packages/@ourworldindata/grapher/src/stackedCharts/StackedDiscreteBarChart.tsx
+++ b/packages/@ourworldindata/grapher/src/stackedCharts/StackedDiscreteBarChart.tsx
@@ -125,6 +125,23 @@ export class StackedDiscreteBarChart
 {
     base: React.RefObject<SVGGElement> = React.createRef()
 
+    private applyMissingDataStrategy(table: OwidTable): OwidTable {
+        if (this.missingDataStrategy === MissingDataStrategy.hide) {
+            // If MissingDataStrategy is explicitly set to hide, drop rows (= times) where one of
+            // the y columns has no data
+            return table.dropRowsWithErrorValuesForAnyColumn(this.yColumnSlugs)
+        } else if (this.missingDataStrategy === MissingDataStrategy.auto) {
+            // If MissingDataStrategy is set to auto, drop rows where there is only a single non-error value
+            if (this.yColumnSlugs.length > 1) {
+                return table.dropRowsWithAtLeastThisManyErrorValuesForColumns(
+                    this.yColumnSlugs,
+                    this.yColumnSlugs.length - 1
+                )
+            }
+        }
+        return table
+    }
+
     transformTable(table: OwidTable): OwidTable {
         if (!this.yColumnSlugs.length) return table
 
@@ -144,11 +161,7 @@ export class StackedDiscreteBarChart
             table = table.interpolateColumnWithTolerance(slug)
         })
 
-        // If MissingDataStrategy is explicitly set to hide, drop rows (= times) where one of
-        // the y columns has no data
-        if (this.missingDataStrategy === MissingDataStrategy.hide) {
-            table = table.dropRowsWithErrorValuesForAnyColumn(this.yColumnSlugs)
-        }
+        table = this.applyMissingDataStrategy(table)
 
         if (this.manager.isRelativeMode) {
             table = table.toPercentageFromEachColumnForEachEntityAndTime(
@@ -165,9 +178,7 @@ export class StackedDiscreteBarChart
             .replaceNegativeCellsWithErrorValues(this.yColumnSlugs)
             .dropRowsWithErrorValuesForAllColumns(this.yColumnSlugs)
 
-        if (this.missingDataStrategy === MissingDataStrategy.hide) {
-            table = table.dropRowsWithErrorValuesForAnyColumn(this.yColumnSlugs)
-        }
+        table = this.applyMissingDataStrategy(table)
 
         return table
     }