vector manipulations

No problems with it working.  The main problem I have observed is
unrealistic expectations.  People write an *essentially* non-vectorized
function and expect Vectorize to produce a version of it which will
out-perform explicit loops every time.  No magic bullets in this game.

Bill. 


Bill Venables
CSIRO Laboratories
PO Box 120, Cleveland, 4163
AUSTRALIA
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http://www.cmis.csiro.au/bill.venables/ 

-----Original Message-----
From: Duncan Murdoch [mailto:murdoch at stats.uwo.ca] 
Sent: Wednesday, 5 March 2008 9:36 AM
To: Venables, Bill (CMIS, Cleveland)
Cc: r-help at r-project.org
Subject: Re: [R] vector manipulations

Your problem is that your function log1( , ) is not vectorized with
respect to its arguments.  For a function to work in outer(...) it

must

accept vectors for its first two arguments and it must produce a
parallel vector of responses.  

To quote the help information for outer:

"FUN is called with these two extended vectors as arguments.

Therefore,

it must be a vectorized function (or the name of one), expecting at
least two arguments."

Sometimes Vectorize can be used to make a non-vectorized function into

a

vectorized one, but the results are not always entirely satisfactory

in

my experience. 

What problems have you seen?

Duncan Murdoch