Added array_mean, array_median expression functions

resources/function_help/json/array_mean

@@ -0,0 +1,11 @@
+{
+  "name": "array_mean",
+  "type": "function",
+  "groups": ["Arrays"],
+  "description": "Returns the mean of arithmetic values in an array. Non numeric values in the array are ignored.",
+  "arguments": [ {"arg":"array","description":"an array"} ],
+  "examples": [ 
+    { "expression":"array_mean(array(0,1,7,66.6,135.4))", "returns":"42"},
+    { "expression":"array_mean(array(0,84,'a','b','c'))", "returns":"42"}
+  ]
+}

resources/function_help/json/array_median

@@ -0,0 +1,11 @@
+{
+  "name": "array_median",
+  "type": "function",
+  "groups": ["Arrays"],
+  "description": "Returns the median of arithmetic values in an array. Non arithmetic values in the array are ignored.",
+  "arguments": [ {"arg":"array","description":"an array"} ],
+  "examples": [ 
+    { "expression":"array_median(array(0,1,42,42,43))", "returns":"42"},
+    { "expression":"array_median(array(0,1,2,42,'a','b'))", "returns":"1.5"}
+  ]
+}

src/core/expression/qgsexpressionfunction.cpp

@@ -5354,6 +5354,63 @@ static QVariant fcnArrayMaximum( const QVariantList &values, const QgsExpression
   return list.isEmpty() ? QVariant() : *std::max_element( list.constBegin(), list.constEnd(), []( QVariant a, QVariant b ) -> bool { return ( qgsVariantLessThan( a, b ) ); } );
 }
 
+static QVariant fcnArrayMean( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QVariantList list = QgsExpressionUtils::getListValue( values.at( 0 ), parent );
+  int i = 0;
+  double total = 0.0;
+  for ( const auto &item : list )
+  {
+    switch ( item.userType() )
+    {
+      case QMetaType::Int:
+      case QMetaType::UInt:
+      case QMetaType::LongLong:
+      case QMetaType::ULongLong:
+      case QMetaType::Float:
+      case QMetaType::Double:
+        total += item.toDouble();
+        ++i;
+        break;
+    }
+  }
+  return i == 0 ? QVariant() : total / i;
+}
+
+static QVariant fcnArrayMedian( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  const QVariantList list = QgsExpressionUtils::getListValue( values.at( 0 ), parent );
+  QVariantList numbers;
+  for ( const auto &item : list )
+  {
+    switch ( item.userType() )
+    {
+      case QMetaType::Int:
+      case QMetaType::UInt:
+      case QMetaType::LongLong:
+      case QMetaType::ULongLong:
+      case QMetaType::Float:
+      case QMetaType::Double:
+        numbers.append( item );
+        break;
+    }
+  }
+  std::sort( numbers.begin(), numbers.end(), []( QVariant a, QVariant b ) -> bool { return ( qgsVariantLessThan( a, b ) ); } );
+  const int count = numbers.count();
+  if ( count == 0 )
+  {
+    return QVariant();
+  }
+  else if ( count % 2 )
+  {
+    return numbers.at( count / 2 );
+  }
+  else
+  {
+    return ( numbers.at( count / 2 - 1 ).toDouble() + numbers.at( count / 2 ).toDouble() ) / 2;
+  }
+}
+
 static QVariant fcnArrayMajority( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
 {
   const QVariantList list = QgsExpressionUtils::getListValue( values.at( 0 ), parent );
@@ -6974,6 +7031,8 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
         << new QgsStaticExpressionFunction( QStringLiteral( "array_last" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ), fcnArrayLast, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_min" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ), fcnArrayMinimum, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_max" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ), fcnArrayMaximum, QStringLiteral( "Arrays" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "array_mean" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ), fcnArrayMean, QStringLiteral( "Arrays" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "array_median" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ), fcnArrayMedian, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_majority" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ), fcnArrayMajority, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_append" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "value" ) ), fcnArrayAppend, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_prepend" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "value" ) ), fcnArrayPrepend, QStringLiteral( "Arrays" ) )

tests/src/core/testqgsexpression.cpp

@@ -1634,17 +1634,25 @@ class TestQgsExpression: public QObject
       QTest::newRow( "with_variable(name:='five', value:=5, expression:=@five * 2)" ) << QStringLiteral( "with_variable(name:='five', value:=5, expression:=@five * 2)" ) << false << QVariant( 10 );
       QTest::newRow( "with_variable('nothing', NULL, COALESCE(@nothing, 'something'))" ) << QStringLiteral( "with_variable('nothing', NULL, COALESCE(@nothing, 'something'))" ) << false << QVariant( "something" );
 
-      // array_first, array_last, array_min, array_max, array_majority
+      // array_first, array_last
       QTest::newRow( "array_first(array('a', 'b', 'c'))" ) << QStringLiteral( "array_first(array('a', 'b', 'c'))" ) << false << QVariant( "a" );
       QTest::newRow( "array_first(array())" ) << QStringLiteral( "array_first(array())" ) << false << QVariant();
       QTest::newRow( "array_last(array('a', 'b', 'c'))" ) << QStringLiteral( "array_last(array('a', 'b', 'c'))" ) << false << QVariant( "c" );
       QTest::newRow( "array_last(array())" ) << QStringLiteral( "array_last(array())" ) << false << QVariant();
+
+      // array_min, array_max, array_mean, array_median, array_majority
       QTest::newRow( "array_min(array())" ) << QStringLiteral( "array_min(array())" ) << false << QVariant();
       QTest::newRow( "array_min(array(-1, 0, 1, 2))" ) << QStringLiteral( "array_min(array(-1, 0, 1, 2))" ) << false << QVariant( -1 );
       QTest::newRow( "array_min(array(make_date(2020,12,11),make_date(2020,12,12),make_date(2020,12,13)))" ) << QStringLiteral( "array_min(array(make_date(2020,12,11),make_date(2020,12,12),make_date(2020,12,13)))" ) << false << QVariant( QDate( 2020, 12, 11 ) );
       QTest::newRow( "array_max(array())" ) << QStringLiteral( "array_max(array())" ) << false << QVariant();
       QTest::newRow( "array_max(array(-1, 0, 1, 2))" ) << QStringLiteral( "array_max(array(-1, 0, 1, 2))" ) << false << QVariant( 2 );
       QTest::newRow( "array_max(array(make_date(2020,12,11),make_date(2020,12,12),make_date(2020,12,13)))" ) << QStringLiteral( "array_max(array(make_date(2020,12,11),make_date(2020,12,12),make_date(2020,12,13)))" ) << false << QVariant( QDate( 2020, 12, 13 ) );
+      QTest::newRow( "array_mean(array())" ) << QStringLiteral( "array_mean(array())" ) << false << QVariant();
+      QTest::newRow( "array_mean(array(0,1,7,66.6,135.4))" ) << QStringLiteral( "array_mean(array(0,1,7,66.6,135.4))" ) << false << QVariant( 42 );
+      QTest::newRow( "array_mean(array(0,84,'a','b','c'))" ) << QStringLiteral( "array_mean(array(0,84,'a','b','c'))" ) << false << QVariant( 42 );
+      QTest::newRow( "array_median(array())" ) << QStringLiteral( "array_median(array())" ) << false << QVariant();
+      QTest::newRow( "array_median(array(0,1,42,42,43))" ) << QStringLiteral( "array_median(array(0,1,42,42,43))" ) << false << QVariant( 42 );
+      QTest::newRow( "array_median(array(0,0,1,2,2,42,'a','b'))" ) << QStringLiteral( "array_median(array(0,0,1,2,2,42,'a','b'))" ) << false << QVariant( 1.5 );
       QTest::newRow( "array_majority(array())" ) << QStringLiteral( "array_majority(array())" ) << false << QVariant();
       QTest::newRow( "array_majority(array(1,2,42,42,'a','b'))" ) << QStringLiteral( "array_majority(array(1,2,42,42,'a','b'))" ) << false << QVariant( QVariantList() << 42 );