I thought I'd share a few workaround routes I've considered (my
attempt at using Amos' Fortran routines failed miserably -- if anyone
is interested i can explain what I tried),
- Ryacas seems to provide a very simple way to evaluate bessel
functions with complex argument,
yacas("N(BesselJ(2, 1+I))")
Complex(0.415798869439e-1,0.247397641513);
Not sure yet how fast this is, and how to get data in/out in R format
but it looks promising.
- Similarly, I get the idea that Sage could provide an interface to
Maxima or Pari and return the desired value. There doesn't seem to be
much of a documentation centred on the use of Sage with R, though.
- Octave has implemented the Amos code (so has Matlab). This should
make it possible to call Octave and get the result back in R (Roctave
package I believe), or better yet, get inspiration to properly use the
underlying Fortran code.
Baptiste
On 9 Nov 2008, at 12:22, baptiste auguie wrote:
Dear all,
I'm writing a code that requires Bessel functions with complex
argument.
Searching the list, I found the continuation of a thread I initiated
a few
months ago:
http://tolstoy.newcastle.edu.au/R/e4/devel/08/03/0746.html
As I understand, the most promising option would be to use the
fortran or C
implementation of Amos,
http://portal.acm.org/citation.cfm?id=214331&dl=GUIDE&coll=GUIDE&CFID=9717168&CFTOKEN=75957024
Sadly, my limited programming skills don't include any knowledge of
fortran,
and I have never managed to link external code to R functions (i'm
missing a
simple example based tutorial, R-ext overwhelms me with information).
A few questions for anyone interested:
- Does the aforementioned fortran code lends itself to an easy
interfacing
with R? (in other words, do I stand a chance in less than 10 years?)
- Is anyone willing to help me with this? The package is hosted on R-
forge
and i could take care of the documentation, etc.
- Is there a package I've missed that already implements this? (one
can
dream)
Many thanks,
baptiste
_____________________________
Baptiste Auguié
School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK
Phone: +44 1392 264187
http://newton.ex.ac.uk/research/emag
______________________________
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<ATT00001.txt>
_____________________________
Baptiste Auguié
School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK
Phone: +44 1392 264187
http://newton.ex.ac.uk/research/emag
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