Vous pouvez déterminer le pic en recherchant la valeur Max pour chaque groupe, puis rechercher la valeur X en recherchant la ligne dans laquelle se trouve la valeur Max.
Voici un exemple de sortie et du script simple qui crée les lignes de référence.

et voici le script
Names Default To Here( 1 );
dt = New Table( "Example",
Add Rows( 130 ),
New Script( "Source", Data Table( "Untitled 25" ) << Sort( By( :Group, :Y ), Order ) ),
New Column( "Group",
Numeric,
"Ordinal",
Format( "Best", 12 ),
Set Values(
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9,
9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11,
11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13,
13, 13]
)
),
New Column( "Y",
Numeric,
"Continuous",
Format( "Best", 12 ),
Set Values(
[1, 2, 3, 6, 7, 7, 8, 8, 8, 10, 1, 2, 2, 3, 5, 5, 6, 7, 8, 10, 1, 3, 3, 5, 6, 7, 8,
10, 10, 10, 2, 3, 3, 3, 4, 4, 7, 9, 9, 9, 1, 1, 2, 3, 6, 6, 7, 8, 8, 10, 1, 1, 3, 3,
3, 4, 6, 6, 8, 8, 2, 3, 4, 5, 5, 7, 9, 9, 10, 10, 2, 2, 2, 4, 5, 6, 7, 9, 10, 10, 1,
1, 2, 3, 3, 4, 8, 9, 9, 10, 1, 3, 3, 4, 4, 4, 4, 7, 8, 10, 2, 3, 4, 5, 6, 7, 8, 8, 8,
9, 2, 5, 5, 6, 7, 8, 8, 9, 10, 10, 2, 3, 4, 4, 6, 6, 8, 8, 9, 9]
)
),
New Column( "X",
Numeric,
"Continuous",
Format( "Best", 12 ),
Set Values(
[1, 2, 3, 4, 5, 6, 10, 9, 7, 8, 1, 2, 3, 4, 5, 6, 10, 9, 7, 8, 1, 2, 3, 4, 5, 6, 10,
9, 7, 8, 1, 2, 3, 4, 5, 6, 10, 9, 7, 8, 1, 2, 3, 4, 5, 6, 10, 9, 7, 8, 1, 2, 3, 4, 5,
6, 10, 9, 7, 8, 1, 2, 3, 4, 5, 6, 10, 9, 7, 8, 1, 2, 3, 4, 5, 6, 10, 9, 7, 8, 1, 2,
3, 4, 5, 6, 10, 9, 7, 8, 1, 2, 3, 4, 5, 6, 10, 9, 7, 8, 1, 2, 3, 4, 5, 6, 10, 9, 7,
8, 1, 2, 3, 4, 5, 6, 10, 9, 7, 8, 1, 2, 3, 4, 5, 6, 10, 9, 7, 8]
)
)
);
// Create the graph
gb = Graph Builder(
Variables( X( :X ), Y( :Y ), Overlay( :Group ) ),
Elements( Points( X, Y, Legend( 9 ) ), Line( X, Y, Legend( 11 ) ) )
);
// Find the number of groups and their max
Summarize( dt, bygroup = by( :group ), theYMax = Max( :Y ) );
// Loop across the groups and create reference lines for the max Y found in each group
For( i = 1, i <= N Items( bygroup ), i++,
theXMax = dt:X[(dt << get rows where( :group == Num( bygroup[i] ) & :Y == theMax[i] ))[1]];
Eval(
Substitute(
Expr(
Report( gb )[AxisBox( 1 )] << add ref line( __x__ );
Report( gb )[AxisBox( 2 )] << add ref line( __y__ );
),
Expr( __x__ ), theXMax,
Expr( __y__ ), theYMax[i]
),
);
);