I agree with everything you say, except that a variable is an ordered
array with a single subscript too, even though that won't help you much
in calculating an outer product.... Also, Mata lets you think it has the
concept of a vector....
Nick
[email protected]
Christopher Baum
To be pedantic, Stata (as opposed to Mata) does not and never has had
vectors. Vectors are ordered arrays with a *single* subscript. There
is no way to create such an object in Stata. You can have matrices
with one row or one column (or both) that look like vectors, but to
use them you must include both a row subscript and a column subscript
in the notation. In that annoying way, Stata's old matrix language
does not allow vectors at all. Mata has the concept of a vector, and
allows you to reference an element as nj[42] rather than nj[42,1] or
nj[1,42]. IMHO this is a good reason to avoid the old matrix language
when you can, as it unnecessarily complicates working with 'real'
vectors such as e(b).
Nick said
Some readers may find Martin's opening sentence a little puzzling,
however. In Stata, as compared with Mata, there is no difficulty in
setting up row or column vectors, which are just matrices with one row
or column. In this sense, Stata has had the idea of vector for several
versions now.
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