Signature Description Parameters

template<typename T>
std::vector<T>
get_col_unique_values(const char *name) const;
        
It returns a vector of unique values in the named column in the same order that exists in the column.
For this method to compile and work, 3 conditions must be met:
  1. Type T must be hash-able. If this is a user defined type, you must enable and specialize std::hash.
  2. The equality operator (==) must be well defined for type T.
  3. Type T must match the actual type of the named column.
Of course, if you never call this method in your application, you need not be worried about these conditions.
T: Data type of the named column
name: Column name
static void test_get_col_unique_values()  {

    std::cout << "\nTesting get_col_unique_values() ..." << std::endl;

    std::vector<unsigned long>  idx =
        { 123450, 123451, 123452, 123453, 123454, 123455, 123456, 123457, 123458, 123459, 123460, 123461, 123462, 123466 };
    std::vector<double> d1 = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 };
    std::vector<double> d2 = { 8, 9, 10, 11, 12, 13, 14, 20, 22, 23, 30, 31, 32, 1.89};
    std::vector<double> d3 = { 15, 16, 15, 18, 19, 16, 21, 0.34, 1.56, 0.34, 2.3, 0.34, 0.89, 19.0 };
    std::vector<int>    i1 = { 22, 23, 24, 25, 99, 100, 101, 3, 2 };
    MyDataFrame         df;

    df.load_data(std::move(idx),
                 std::make_pair("col_1", d1),
                 std::make_pair("col_2", d2),
                 std::make_pair("col_3", d3),
                 std::make_pair("col_4", i1));

    df.write<std::ostream, double, int>(std::cout);
    std::cout << "Getting unique values in column col_3" << std::endl;

    const std::vector<double>   result =
        df.get_col_unique_values<double>("col_3");

    for (auto &iter : result)
        std::cout << iter << ",";
    std::cout << std::endl;
}
C++ DataFrame