There are no "string vectors" in Matlab, but you need a "cell string":
Planets = {'Mercury', 'Venus', 'Earth', 'Mars', 'Jupiter', 'Saturn', 'Uranus', 'Neptune'}
Index = [2, 4, 3];
Chosen = Planets(Index)
See the "Getting Started" chapters of the documentation, because such a powerful tool as Matlab demands for learning the basics from the documentation.
EDITED: And when you really have a good reason not to use a cell string, but a char-matrix:
Chosen = char(Planets(Index))
Now the strings are padded with zeros. But it is less useful to work with char matrices. Prefer cell strings whenever it is possible.
