st: mata: columns of different eltypes in a transmorphic matrix

[László Sándor <sandorl@gmail.com>]

Hi all,

I am confused by some behavior in StataMP 13 on my mac.

I am pretty sure that a transmorphic matrix can have columns (or
simply cells) of different types, as you can easily grab some Stata
data with  st_data and the resulting matrix will hold both strings and
reals according to your Stata variables.

But then I am not sure I understand why Stata complains about joining
transmorphic matrices into a transmorphic matrix if some of them
happen to hold reals and other strings. Why isn't this OK if I mean
the end result to hold cells of both types?

I tried to define a transmorphic placeholder first and fill in the
columns one by one, but if I start with (transmorphic colvectors
happening to be:) real colvectors the code breaks when I get to the
string colvector.

I don't see why this is invalid or why this limitation isn't better
documented. In any case, it would be nice to have a way around this.

Thanks!
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