CSMSL.Chemistry.ChemicalFormulaGenerator.FromMass C# (CSharp) Method

        public IEnumerable<ChemicalFormula> FromMass(double lowMass, double highMass, int maxNumberOfResults = int.MaxValue, bool sort = true)
        {
            if (highMass <= lowMass)
            {
                throw new ArgumentException("The high mass must be greater than the low mass");
            }

            if (!MaximumFormula.Contains(MinimumFormula))
            {
                throw new ArgumentException("The maximum formula must include the minimum formula");
            }

            List<ChemicalFormula> returnFormulas = new List<ChemicalFormula>();

            // The minimum formula required for any return formulas

            double correctedLowMass = lowMass;
            double correctedHighMass = highMass;

            bool minFormulaExists = MinimumFormula.IsotopeCount != 0;
            int[] minValues = null;
            double minFormulaMass = 0;

            if (minFormulaExists)
            {
                minValues = MinimumFormula.GetIsotopes();
                minFormulaMass = MinimumFormula.MonoisotopicMass;

                correctedLowMass -= minFormulaMass;
                correctedHighMass -= minFormulaMass;

                // Add the minimum formula itself if it is within the bounds
            }

            // The maximum formula allowed, represented in number of isotopes
            int[] maxValues = MaximumFormula.GetIsotopes();

            // The current formula represented in isotopes
            int[] currentFormula = new int[maxValues.Length];

            // A list of all the isotopes masses
            double[] masses = new double[maxValues.Length];

            int length = maxValues.Length;

            for (int j = 0; j < length; j++)
            {
                if (minFormulaExists && j < minValues.Length)
                    maxValues[j] -= minValues[j];
                if (maxValues[j] == 0)
                    continue;
                masses[j] = PeriodicTable.GetIsotope(j).AtomicMass;
            }
            masses[0] = PeriodicTable.GetIsotope(0).AtomicMass;

            GenerateFormulaHelper(correctedLowMass, correctedHighMass, masses, maxValues, length - 1, currentFormula, returnFormulas);

            if (minFormulaExists)
            {
                foreach (ChemicalFormula formula in returnFormulas)
                {
                    formula.Add(MinimumFormula);
                }
                if (minFormulaMass >= lowMass && minFormulaMass <= highMass)
                {
                    returnFormulas.Add(new ChemicalFormula(MinimumFormula));
                }
            }

            if (!sort)
                return returnFormulas;
            double meanValue = (highMass + lowMass)/2.0;
            return returnFormulas.OrderBy(formula => Math.Abs(formula.MonoisotopicMass - meanValue)).Take(maxNumberOfResults);
        }

        private static void ChemicalFormulaGeneratorExample()
        {
            //// Create a generator with formula bounds. In this case, every formula needs to have at least H2 but no more than C4H2
            //ChemicalFormulaGenerator generator = new ChemicalFormulaGenerator(new ChemicalFormula("H2"), new ChemicalFormula("C4H2"));

            //var formulas = generator.FromMass(0, 100).ToList();
            //foreach (var formula in formulas)
            //{
            //    WriteFormulaToConsole(formula);
            //}

            //Console.WriteLine("Unique Formulas: " + formulas.Count);

            // Create a generator with formula bounds. In this case, every formula needs to have at least H2 but no more than C4H2
            ChemicalFormulaGenerator generator = new ChemicalFormulaGenerator(new ChemicalFormula("C10000N1000H1000O1000"));

            DoubleRange range = DoubleRange.FromPPM(new ChemicalFormula("C62H54N42O24").MonoisotopicMass, 0.1);
            double mass = range.Mean;
            int count = 0;
            foreach (var formula in generator.FromMass(range).Validate())
            {
                Console.WriteLine("{0,-15} {1:F10} {2,-5:G5} ppm", formula, formula.MonoisotopicMass,
                    Tolerance.GetTolerance(formula.MonoisotopicMass, mass, ToleranceUnit.PPM));
                count++;
            }
            Console.WriteLine("Unique Formulas: " + count);
        }