[R] vector manipulations

[Bill.Venables at csiro.au]

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
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-----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

On 3/4/2008 5:41 PM, Bill.Venables at csiro.au wrote:
> 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