# Degree of freedom input for Monte Carlo simulation of asset returns with multivariate t distribution

How do I calculate or estimate the degrees of freedom in order to perform a Monte Carlo simulation of asset returns with multivariate t distribution using R functions? I am able to calculate the mean vector of asset returns mu, as well as the covariance matrix covmat of asset returns. I also understand that Sigma is the scale matrix which is covmat * df/(df-2)

library(mvtnorm)
sim <- rep(mu, each = n) + rmvt(n, sigma=Sigma, df=df)
#df is degrees of freedom, which is a required input in the function rmvt and
required to calculate the scale matrix