impose internal coherence (positive definite) on a matrix

#1
how do I turn a matrix which bears the resemblance of a variance covariance matrix into a "positive definite" matrix (=a usable var cov matrix) ?

is there any way?
 

spunky

Doesn't actually exist
#2
is there any particular reason as for why you're not using an actual positive definite matrix? or an actual covariance matrix that satisfies this and other properties?