None of those three functions are supported by HDL Coder, as you seem aware. Think about what you are trying to accomplish; are you really wanting to implement a random number generator in your FPGA? Perhaps the call to rand() can exist inside your testbench, and the data from it can be an input to your hardware design.
For involved matrix calculations such as eig(|) and |cov(), you will need to decompose these to the underlying algorithm. This is certainly doable, if a bit involved, and will be supported by HDL Coder. Since you are working with a fixed size array, you have the chance to optimize your implementation for the sizes involved, should the opportunity arise.
