private IEnumerable <Pair <string, Dictionary <string, SufficientStatistics> > > CreateNameAndCaseIdToNonMissingValueEnumeration(string predictorSparseFileName, bool speedOverMemory)
        {
            //Dictionary<string, Dictionary<string, SufficientStatistics>> predictorVariableToCaseIdToRealNonMissingValue = LoadSparseFileInMemory(predictorSparseFileName);
            IEnumerable <Pair <string, Dictionary <string, SufficientStatistics> > > predictorNameAndCaseIdToNonMissingValueEnumeration;

            if (speedOverMemory)
            {
                Dictionary <string, Dictionary <string, SufficientStatistics> > predictorVariableToCaseIdToRealNonMissingValue = LoadSparseFileInMemory(predictorSparseFileName);
                predictorNameAndCaseIdToNonMissingValueEnumeration = SpecialFunctions.DictionaryToPairEnumeration(predictorVariableToCaseIdToRealNonMissingValue);
            }
            else
            {
                predictorNameAndCaseIdToNonMissingValueEnumeration = LoadSparseFileEnumeration(predictorSparseFileName);
            }
            return(predictorNameAndCaseIdToNonMissingValueEnumeration);
        }