The following suboptions may be used within the mgroups(),
mlabels(), collabels(), eqlabels(),
varlabels(), and stats(, labels()) options:

none suppresses the printing of the labels or drops the
part of the table heading to which it applies.

prefix(<string>) specifies a common prefix to be added to each
label.

suffix(<string>) specifies a common suffix to be added to each
label.

begin(<string>) specifies a prefix to be printed at the
beginning of the part of the table to which it applies. If begin is
specified in varlabels() or stats(,labels()), the prefix will
be repeated for each regressor or summary statistic.

end(<string>) specifies a suffix to be printed at the end of the
part of the table to which it applies. If end is specified in
varlabels() or stats(,labels()), the suffix will be repeated
for each regressor or summary statistic.

last specifies that the last occurrence of the end()-suffix in
varlabels() or stats(,labels()) be printed. This
is the default. Use nolast to suppress the last occurrence of the
suffix.

span causes labels to span columns, i.e. extends the labels across
several columns, if appropriate. This suboption is relevant only for the
mgroups(), mlabels(), eqlabels(), and
collabels() options. The @span string returns the number of
spanned columns if it is included in the label, prefix, or suffix. A LaTeX example:

. estout ..., mlabels(, span prefix(\multicolumn{@span}{) suffix(}))

erepeat(<string>) specifies a string that is repeated for each
group of spanned columns at the very end of the row if the span
suboption is specified. This suboption is relevant only for the
mgroups(), mlabels(), eqlabels(), and
collabels() options. If the @span string is included in
string it will be replaced by the range of columns spanned. A LaTeX example:

. estout ..., mlabels(, span erepeat(\cline{@span}))

lhs(<string>) inserts string into the otherwise empty cell
in the left stub of the row of the table heading to which it applies. This
suboption is relevant only for the mgroups(), mlabels(),
eqlabels(), and collabels() options.