Gets the add element attribute if it exists. If non-existant it will return NULL.
prAttr4RgroupAdd(rgroup, rgroup_iterator, no_cols)
A vector of character strings containing headings for row groups.
n.rgroup
must be present when rgroup
is given. See
detailed description in section below.
The rgroup number of interest
The ncol(x)
of the core htmlTable x argument