search for: pacin

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2012 May 16
1
Optimization problem
Hi, I'm dealing with an optimization problem. I'm using 'optim' to maximize the output of a function, given some restrictions on the input. I would like to know if there is a way to impose some restrictions on 'intermediate variables' of the function. An example.. fx = function (x) { s <- 0 for (i in 1:3) { s <- x[i]^3 + s } s } optim(rep(4,3),
2011 Nov 18
1
Ensuring a matrix to be positive definite, case involving three matrices
Hi, I would like to know what should I garantee about P and GGt in order to have F = Z %*% P %*% t(Z) + GGt always as a positive definite matrix. Being more precise: I am trying to find minimum likelihood parameters by using the function 'optim' to find the lowest value generated by $LogLik from the function 'fkf' (http://127.0.0.1:27262/library/FKF/html/fkf.html). The