Sum n largest numbers EPPlus

Question

I'm trying to sum the n largest numbers of a range.

My formula is: SUM(LARGE(A10:A15, {1,2}))

But I'm getting a #VALUE as result.

If I debug the formula execution to a log file I got that:

Worksheet: Sheet 1
Address: A9
OfficeOpenXml.FormulaParsing.Exceptions.ExcelErrorValueException: #VALUE!
   em OfficeOpenXml.FormulaParsing.Excel.Functions.IntArgumentParser.Parse(Object obj)
   em OfficeOpenXml.FormulaParsing.Excel.Functions.ExcelFunction.ArgToInt(IEnumerable`1 arguments, Int32 index)
   em OfficeOpenXml.FormulaParsing.Excel.Functions.Math.Large.Execute(IEnumerable`1 arguments, ParsingContext context)
   em OfficeOpenXml.FormulaParsing.ExpressionGraph.FunctionCompilers.DefaultCompiler.Compile(IEnumerable`1 children, ParsingContext context)
   em OfficeOpenXml.FormulaParsing.ExpressionGraph.FunctionExpression.Compile()

Looks like the Large Function doesn't accept an array as a second argument.

How can I get the sum of n largest values formula in EPPlus?

Answer 1

Looks like this kind of formula only works when save the excel to file. In my case I don't want a file, just the calculated value.

The solution was to extend de ExcelFunction class and create my own implementation:

public class SumLargest: ExcelFunction
{

    public override CompileResult Execute(IEnumerable<FunctionArgument> arguments, ParsingContext context)
    {
        ValidateArguments(arguments, 2);

        //n largest values
        var n = ArgToInt(arguments, 1);

        var cells = ArgsToDoubleEnumerable(arguments, context);

        var values = cells.ToList();
        values.RemoveAt(values.Count() - 1);

        var result = values
            .OrderByDescending(x => x)              
            .Take(n)
            .Sum();

        return CreateResult(result, DataType.Decimal);
    }

}

Then I added it to my package:

using (ExcelPackage excelPackage = new ExcelPackage())
{
     excelPackage.Workbook.FormulaParserManager.AddOrReplaceFunction("SUMLARGEST", new SumLargest());
     ....
}

And I can use it in a much better way then the original formula:

Cells["C5"].Formula = "SUMLARGEST(A10:A15, 2)"

Reference: https://github.com/JanKallman/EPPlus/wiki/Implementing-missing-or-new-Excel-functions