Signature Description Parameters
templat<typename T, typename I = unsigned long, typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type>
struct CovVisitor;
This functor class calculates the covariance of two given columns. In addition, it provides the variances of both columns.
        explicit CovVisitor(bool bias = true, bool skipnan = true);
        
See this document and dataframe_tester.cc for examples.
T: Column data type. T must be an arithmetic-enabled type
I: Index type.