[R] Nelder-Mead with output of simplex vertices

[Terry Therneau]

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Greetings!
I want to follow the evolution of a Nelder-Mead function
minimisation (a function of 2 variables). Hence each simplex
will have 3 vertices.

Therefore I would like to have a function which can output
the coordinates of the 3 vertices after each new simplex
is generated. However, there seems to be no way (which I can
detect) of extracting this information from optim() (the 'trace'
argument to 'control' does not seem to have provision for this,
according to '?optim', and I have tried it out without success).

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 Why not put a cat() statement into "fn", the function that you supply
which optim is calling?  That will give the vertices that it tries one
by one.

Terry T.