Hi, there.

 

How do I calculate the cross-product in the form of
\sum_{i=1}^{n}X_{i}^{t} \Sigma X_{i} using R code without using do loop?
X_{i} is the covariate matrix for subject I, \Sigma is the covariance
matrix.

 

Thanks for your help.

 

Yulei

 


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