[Rsiena-help] clarification on varying covariates waves / fixed parameter for cycle4 effect

[marco tonellato]

Dear all,

while importing attribute data into my model I've noticed a difference
between the RSiena manual  and the help of the function "varCovar" regarding
the number of covariate waves that must be imported:

In the RSiena manual
- paragraph 4.3 ("individual covariates"): "If observation moments for the
network are t1, t2, ..., tM, then the changing covariates should refer to
the M-1 moments t1 through tM -1, and the m-th value of the changing
covariates is assumed to be valid for the period from moment tm to moment
tm+1. The value at tM, the last moment, does not play a role".

Whereas in the varCovar help
- Arguments: val: Matrix of covariate values, one row for each actor, one
column for each period.

I noticed that RSiena takes M-1 columns, leaving out the last one.

What it is not clear to me is whether individual changing covariates should
be measured at each time period or, ideally, between each of the time
periods (consequently  assuming one value for each time period minus 1).
Could you please clarify on this? How should the varCovar columns be coded?


Coming to a different topic, I noticed that the 4-cycles effect requires a
parameter to be set, but in the 4cycle statistic there seems to be no such
fixed parameter.
Could you please clarify on this as well? What role does this fixed
parameter play in the estimation?

Thanks a lot,

Marco
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