vec, vech, invvec, invvech {ks} | R Documentation |
The vec (vector) operator takes a d x d matrix and stacks the columns into a single vector of length d^2. The vech (vector half) operator takes a symmetric d x d matrix and stacks the lower triangular half into a single vector of length d(d+1)/2.
The functions invvec and invvech are the inverses of vec and vech i.e. they form matrices from vectors.
vec(x) vech(x) invvec(x) invvech(x)
x |
vector or matrix |
Wand, M.P. & Jones, M.C. (1995) Kernel Smoothing. Chapman & Hall. London.
x <- matrix(1:9, nrow=3, ncol=3) vec(x) vech(x) invvec(vec(x)) invvech(vech(x))