C++ to C conversion

[raj@12345]

Hi,

I am new for C++ coding , I have tried to convert (std::vector < std::vector< double > > a data type variable into two dimensional double pointer in c but it gives

Compilation error. Please could anyone help explain me that how to convert (std::vector < std::vector< double > > a. data type variable into two dimensional double pointer in c

Thanks
Raj