[R] help please >>metro_hastings function

[hms Dreams]

Hi :)anybody can help me please I'm trying to use Metro_Hastings (

MHadaptive package)the proplem is:  How can I know the covariance matrix( prop_sigma ) to enter it in Metro_Hastings: 
 mcmc_r=Metro_Hastings(li_func=baysianlog, pars=c(1,1,1), prop_sigma =NULL,par_names=c('alpha','gamma','delta'),data=x ) its gave me an error , I must enter the cov matrix but I don't know how to calculate it, somebody told me to wrote the function without prop_sigma but its also gave me an error what can I do?? Thank you,Sara
 		 	   		  
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