Understanding index column in a StdDataFrame<I> and templating

[dereckmezquita]

One thing I've not understood from the docs is why template the index type for a DataFrame? I can understand using certain types for the index column such as int/uin64_t/DateTime etc. It makes sense to me that these should be unique values (DateTime might not).

However it is also valid to create a StdDataFrame<bool>. Can such a construct have a use?

std::vector<double> dblvec2 = { 0.998, 0.3456, 0.056, 0.15678, 0.00345, 0.923, 0.06743, 0.1 };
std::vector<std::string> strvec = { "Col_name", "Col_name", "Col_name", "Col_name", "Col_name" };

StdDataFrame<bool> df2;
df2.load_data(std::move(idx_bool),
    std::make_pair("dbl_col_2", dblvec2),
    std::make_pair("str_col", strvec));

I just want to better understand some of the reasoning/use; the why behind the way DataFrame was built and the data structures behind it.

I'm in the process of learning so thank you.

[hosseinmoein]

An index column in a DataFrame is unlike an index in a SQL table. SQL table index makes access efficient. It doesn’t give you any more information. The index column in a DataFrame is metadata about the data in the DataFrame. Each entry in the index describes the given row. It could be time, frequency, …, or a set of descriptors in a struct (like temperature, altitude, …). So, there can be almost infinite possibilities. That’s why I kept the index column as a template which also differentiates the DataFrame type.
Whether a bool index column type is relevant or not is unimportant.