Some Tools for Handling Symmetric Matrices
sm2vec takes a symmetric matrix and puts
the lower triagonal entries into a vector (cf. lower.tri).
sm.index lists the corresponding x-y-indices for each entry
in the vector produced by sm2vec.
vec2sm reverses the operation by sm2vec and converts the
vector back to a symmetric matrix. If diag=FALSE the
diagonal of the resulting matrix will consist of NAs. If order
is supplied then the input vector vec will first be rearranged accordingly.
sm2vec(m, diag = FALSE) sm.index(m, diag = FALSE) vec2sm(vec, diag = FALSE, order = NULL)
m |
symmetric matrix |
diag |
logical. Should the diagonal be included in the conversion to and from a vector? |
vec |
vector of unique elements from a symmetric matrix |
order |
order of the entries in |
A vector (sm2vec), a two-column matrix with indices (sm.index),
or a symmetric matrix (vec2sm).
Korbinian Strimmer (https://strimmerlab.github.io/).
# load corpcor library
library("corpcor")
# a symmetric matrix
m = rbind(
c(3,1,1,0),
c(1,3,0,1),
c(1,0,2,0),
c(0,1,0,2)
)
m
# convert into vector (including the diagonals)
v = sm2vec(m, diag=TRUE)
v.idx = sm.index(m, diag=TRUE)
v
v.idx
# put back to symmetric matrix
vec2sm(v, diag=TRUE)
# convert from vector with specified order of the elements
sv = sort(v)
sv
ov = order(v)
ov
vec2sm(sv, diag=TRUE, order=ov)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.