For values of pow other than
0 , this term adds one network statistic to the model,
equaling the sum, over directed edges \((i,j)\) , of
sign.action(attr[i]-attr[j])^pow if dir is
"t-h" and of sign.action(attr[j]-attr[i])^pow if
"h-t" . That is, the
argument dir determines which vertex's attribute is
subtracted from which, with tail being the origin of a directed edge
and head being its destination, and bipartite networks' edges being
treated as going from the first part (b1) to the second (b2).
If pow==0 , the exponentiation is replaced by the signum
function: +1 if the difference is positive, 0 if there
is no difference, and -1 if the difference is negative. Note
that this function is applied after the
sign.action . The comparison is exact, so when using
calculated values of attr , ensure that values that you
want to be considered equal are, in fact, equal.
# binary: diff(attr, pow=1, dir="t-h", sign.action="identity")# valued: diff(attr, pow=1, dir="t-h", sign.action="identity", form ="sum")
a vertex attribute specification (see Specifying Vertex attributes and Levels (?nodal_attributes) for details.)
exponent for the node difference
determines which vertix's attribute is subtracted from which. Accepts: "t-h" (the default), "tail-head" , "b1-b2", "h-t" , "head-tail" , and "b2-b1" .
one of "identity", "abs", "posonly", "negonly". The following sign.actions are possible:
"identity" (the default) no transformation of the
difference regardless of sign
"abs" absolute value of the difference: equivalent
to the absdiff term
"posonly" positive differences are kept, negative
differences are replaced by 0
"negonly" negative differences are kept, positive
differences are replaced by 0
how to aggregate tie values in a valued ERGM: "sum"
(the default) for a statistic of the form \(\sum_{i,j} x_{i,j}
y_{i,j}\), where \(y_{i,j}\) is
the value of dyad \((i,j)\) and \(x_{i,j}\) is the
term's covariate associated with it; and "nonzero" with the
edge considered to be present if its value is not 0. See
ergmTerm for more information.
ergmTerm for index of model terms currently visible to the package.
ergm:::.formatTermKeywords("ergmTerm", "diff", "subsection")