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Signature Description Parameters 
template<arithmetic T, typename ... Ts>
DataFrame
get_data_by_stdev(const char *col_name,
                  T high_stdev,
                  T low_stdev) const;
This calculates the mean and standard deviation of the named column. It returns a new DataFrame that contains all the data where named column data is between high_stdev and low_stdev from the mean.
Self is unchanged.

NOTE Type T must support arithmetic operations
 T: Type of the named column
Ts: The list of types for all columns. A type should be specified only once
col_name: Name of the data column
high_stdev: All data rows below this will be returned.
low_stdev: All data rows above this will be returned.
 
template<arithmetic T, typename ... Ts>
PtrView
get_view_by_stdev(const char *col_name,
                  T high_stdev,
                  T low_stdev);
This is identical to above get_data_by_stdev(), but:
  1. The result is a view
  2. Since the result is a view, you cannot call make_consistent() on the result.
NOTE: There are certain operations that you cannot do with a view. For example, you cannot add/delete columns, etc.
 T: Type of the named column
Ts: The list of types for all columns. A type should be specified only once
col_name: Name of the data column
high_stdev: All data rows below this will be returned.
low_stdev: All data rows above this will be returned.
 
template<arithmetic T, typename ... Ts>
ConstPtrView
get_view_by_stdev(const char *col_name,
                  T high_stdev,
                  T low_stdev) const;
Same as above view, but it returns a const view. You can not change data in const views. But if the data is changed in the original DataFrame or through another view, it is reflected in the const view. T: Type of the named column
Ts: The list of types for all columns. A type should be specified only once
col_name: Name of the data column
high_stdev: All data rows below this will be returned.
low_stdev: All data rows above this will be returned.
 
static void test_get_data_by_stdev()  {

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

    typedef StdDataFrame64<std::string> StrDataFrame;

    StrDataFrame    df;

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

    StrDataFrame    df2 = df;

    auto    lbd = [](const std::string &, const double &) -> bool { return (true); };
    auto    view = df2.get_view_by_sel<double, decltype(lbd), double, long>("IBM_Open", lbd);

    auto    result_df = df.get_data_by_stdev <double, double, long>("IBM_Close", 0.1, -0.4);
    auto    result_view = view.get_view_by_stdev<double, double, long>("IBM_Close", 0.1, -0.4);

    assert(result_df.get_index().size() == 379);
    assert(result_view.get_index().size() == 379);
    assert(result_view.get_column<double>("IBM_Open").size() == 379);
    assert(result_view.get_column<long>("IBM_Volume").size() == 379);
    assert(result_df.get_column<double>("IBM_Low").size() == 379);
    assert(result_df.get_column<long>("IBM_Volume").size() == 379);
    assert(result_df.get_index()[300] == "2018-08-23");
    assert(result_view.get_index()[300] == "2018-08-23");
    assert(result_df.get_index()[101] == "2016-06-13");
    assert(result_view.get_index()[101] == "2016-06-13");
    assert(result_view.get_column<double>("IBM_Open")[45] == 141.740005);
    assert(result_df.get_column<double>("IBM_Open")[45] == 141.740005);
    assert(result_df.get_column<long>("IBM_Volume")[230] == 4413200);
    assert(result_view.get_column<long>("IBM_Volume")[230] == 4413200);
}

C++ DataFrame