symmetrize {netseg}

(De)symmetrize square numeric matrix

Description

(De)symmetrize square binary matrix in various ways.

Usage

symmetrize(mat, rule = c("upper", "lower", "div", "intdiv"))

Arguments

mat

square numeric matrix

rule

character, direction of copying, see Details

Details

Argument mat is to be a square numeric matrix. The way it is made symmetric, or asymetric, depends on the value of the rule argument.

If rule is "upper" or "lower" then mat is made symmetric by copying, respectively, upper triangle onto lower, or lower onto upper. The value of rule specifies values of which triangle will stay in the returned value.

If rule is "intdiv" then the off-diagonal values are distributed approximately equally between the lower/upper triangles. If r is the computed result, then r[i,j] will be equal to ⁠(x[i,j] + x[j,i]) \%/\% 2⁠ if r[i,j] is in the lower triangle. It will be equal to ⁠(x[i,j] + x[j,i]) \%/\% 2 + 1⁠ if in the upper triangle.

If rule is "div" then the off-diagonal values are distributed equally between the lower/upper triangles: as with "intdiv" but using normal / division.

Value

A matrix: symmetrized version of mat.

See Also

fold()

Examples

m <- matrix(1:16, 4, 4)

# copy upper triangle onto lower symmetrically
symmetrize(m, "upper")

# copy lower triangle onto upper symmetrically
symmetrize(m, "lower")

# distribute off-diagonal values exactly
# r[i,j] = (m[i,j] + m[j,i]) / 2
r1 <- symmetrize(m, "div")
r1
all.equal(sum(m), sum(r1))

# distribute off-diagonal values using integer division
r2 <- symmetrize(m, "intdiv")
r2
all.equal(sum(m), sum(r2))