I need to use the mvnrnd function in matlab to generate random monthly returns for a set of assets. However, I am a bit confused about how to use this function to do it since it asks me MU and SIGMA values. How should I pick these values ?
MU and SIGMA are usually estimated from historical data. For example, you can take time series of returns on your asset and compute their sample means (which will be stacked in your MU vector) and their sample covariance matrix (your SIGMA matrix). If the returns to K assets observed over T periods are stored in a KxT matrix R, then the MATLAB commands are: