setXPtr {rrp} | R Documentation |
Sets the elements of a XPtr object to a constant vector-wise. The idea is that
a symmetrix matrix M
can be represented as a triangular object d
.
With this function you set M[x,x] = k
but instead of working on
M
this function works on its dist
representation d
.
setXPtr(d, x, k)
d |
a XPtr object, lower diagonal, representing a symmetric matrix |
x |
a list of vectors of indices |
k |
a vector of constants to add, arguments are eventually recycled silently |
returns the modified dist object
S. M. Iacus
M <- matrix(0,5,5) d <- newXPtr(5, 0) x <- list(1:3,4:5) setXPtr(d,x,c(1,2)) # which is the equivalent of (apart for the diagonal elements) M[1:3,1:3] <- 1 M[4:5,4:5] <- 2 # Indeed, we have (XPtrToDist(d)) as.dist(M)