code: public double reduce(String numberColumnName, NumericAggregateFunction function) {
          NumberColumn<?> column = table.numberColumn(numberColumnName);
          return function.summarize(column.where(selection));
      }
docs: Returns the result of applying the given function to the specified column
  
  @param numberColumnName The name of a numeric column in this table
  @param function         A numeric reduce function
  @return the function result
  @throws IllegalArgumentException if numberColumnName doesn't name a numeric column in this table