Whenever you are repeating the same operation multiple times, and without inputs, think about using replicate
. Here you can use it twice:
SimNo <- 10
det1 <- replicate(SimNo, {
X <- replicate(6, rnorm(1000, 0, 1))
sx <- scale(X) / sqrt(999)
det(t(sx) %*% sx)
})
detans <- ifelse(det1 < 1, det1, 0)
Otherwise, this is what your code should have looked with your for
loop. You needed to create a vector for storing your outputs at each loop iteration:
SimNo <- 10
detans <- numeric(SimNo)
for (i in 1:SimNo) {
z1<-rnorm(1000,0,1)
z2<-rnorm(1000,0,1)
z3<-rnorm(1000,0,1)
z4<-rnorm(1000,0,1)
z5<-rnorm(1000,0,1)
z6<-rnorm(1000,0,1)
X<-cbind(z1,z2,z3,z4,z5,z6)
sx<-scale(X)/sqrt(999)
det1<-det(t(sx)%*%sx)
detans[i] <- ifelse(det1<1,det1,0)
}
Edit: you asked in the comments how to access X
using replicate
. You would have to make replicate
create and store all your X
matrices in a list. Then use the *apply
family of functions to loop throughout that list to finish the computations:
X <- replicate(SimNo, replicate(6, rnorm(1000, 0, 1)), simplify = FALSE)
det1 <- sapply(X, function(x) {
sx <- scale(x) / sqrt(999)
det(t(sx) %*% sx)
})
detans <- ifelse(det1 < 1, det1, 0)
Here, X
is now a list of matrices, so you can get e.g. the matrix for the second simulation by doing X[[2]]
.