From help-octave-request at bevo dot che dot wisc dot edu Wed Jan 14 15:53:05 2004
Subject: Re: C++ and octave
From: Geraint Paul Bevan <g dot bevan at mech dot gla dot ac dot uk>
To: =?ISO-8859-1?Q?S=F8ren_Hauberg?= <soren at hauberg dot org>
CC: help-octave at bevo dot che dot wisc dot edu
Date: Wed, 14 Jan 2004 21:59:45 +0000

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Søren Hauberg wrote:
| Hi
| Thanks for the quick reply, and I'm sorry about my late reply
|
| A method that I need to implement on C++ needs to compute the mean and
| standard deviation of the values in a matrix. I cannot find any
| functions I can call from C++ to compute these values and google gives
| me nothing.
|
| Typing "type mean" inside octave gives me an m-file implementation of
| the mean function. Does this mean I can't call mean from C++ ?
| At the moment I have just a quick 'n' dirty implementation of mean & std
| in C++. Is this really the way to go?
|
| Soren
|

You can call any Octave function (.m or .oct) from C++ DLD functions
using "feval". Of course, there will probably be a fairly significant
overhead compared to coding the function directly in C++ as the Octave
interpreter has to be invoked.

The (quick and dirty) code below demonstrates how you can call the
"mean" function from a DLD:

geraint at pavilion:~/mean$ cat my_mean.cc

#include <octave/oct.h>
#include <octave/parse.h>

DEFUN_DLD (my_mean, args, , "mean")
{
~  octave_value_list retval;
~  double mean;
~  mean = feval ("mean", args(0))(0).double_value();
~  retval(0) = mean;
~  return retval;
}

geraint at pavilion:~/mean$ mkoctfile my_mean.cc
geraint at pavilion:~/mean$| echo "mean([1,2,5]) , my_mean([1,2,5])"  echo "mean([1,2,5]) , my_mean([1,2,5])" | octave -q
ans = 2.6667
ans = 2.6667

- --
Geraint Bevan
http://homepage.ntlworld.com/geraint.bevan

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