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Signature	Description	Parameters
template<typename OTHER, typename ... Ts> DataFrame & assign(const OTHER &rhs); template<typename OTHER, typename ... Ts> DataFrame & assign(OTHER &rhs);	The purpose of assign() is to make it possible to copy any version of DataFrame to any other version. It means you can assign a View to a DataFrame or assign a PtrView to a View and so on and so forth. assign() copies the data from rhs to self. It returns a reference to self.	OTHER: DataFrame type of rhs Ts: List all the types of all data columns. A type should be specified in the list only once. rhs: DataFrame instance that's copied from

static void test_view_assign()  {

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

    typedef StdDataFrame64<std::string> StrDataFrame;

    StrDataFrame    df;

    try  {
        df.read("SHORT_IBM.csv", io_format::csv2);
    }
    catch (const DataFrameError &ex)  {
        std::cout << ex.what() << std::endl;
    }

    auto    lbd = [](const std::string &, const double &) -> bool { return (true); };
    auto    ptr_view = df.get_view_by_sel<double, decltype(lbd), double, long>("IBM_Open", lbd);
    auto    view = df.get_view_by_loc<double, long>(Index2D<long>{ 100, 500 });

    StrDataFrame    df2;
    StrDataFrame    df3;

    df2.assign<decltype(ptr_view), double, long>(ptr_view);
    df3.assign<decltype(view), double, long>(view);

    assert(df2.get_index().size() == 1721);
    assert(df3.get_index().size() == 400);
    assert(std::fabs(df2.get_column<double>("IBM_Open")[100] - 184.48) < 0.001);
    assert(df3.get_column<long>("IBM_Volume")[100] == 4350200);

    StrDataFrame::View      dfv;
    StrDataFrame::PtrView   dfpv;

    dfv.assign<StrDataFrame, double, long>(df2);
    dfpv.assign<StrDataFrame, double, long>(df3);
    assert(dfv.get_index().size() == 1721);
    assert(dfpv.get_index().size() == 400);
    assert(std::fabs(dfv.get_column<double>("IBM_Open")[100] - 184.48) < 0.001);
    assert(dfpv.get_column<long>("IBM_Volume")[100] == 4350200);

    StrDataFrame::View      dfv2;
    StrDataFrame::PtrView   dfpv2;

    dfv2.assign<decltype(dfpv), double, long>(dfpv);
    dfpv2.assign<decltype(dfv), double, long>(dfv);
    assert(dfv2.get_index().size() == 400);
    assert(dfpv2.get_index().size() == 1721);
    assert(std::fabs(dfv2.get_column<double>("IBM_Open")[100] - 181.24) < 0.001);
    assert(dfpv2.get_column<long>("IBM_Volume")[100] == 3721600);
}