Re: Bi variate to mono variate functions

[Geordie McBain]

Yes, you can use global, or also inline (in case you're worried about
the things that might go wrong if you leave a global variable called x
lying around):

  octave2.9:1> function z = g (x, y), z = x.^2+y.^2; endfunction
  octave2.9:2> quad (inline ("g (1, y)"), 0, 1)
  ans = 1.3333
  octave2.9:3> quad (inline ("g (2, y)"), 0, 1)
  ans = 4.3333
  octave2.9:4> quad (inline ("g (0, y)"), 0, 1)
  ans = 0.33333

I was going to write about these two solutions at wiki.octave.org but it
seems from David Bateman's post that this will only be of historical
interest.  (Well done, David.)

On Wed, 2006-03-29 at 11:41 +0000, Thomas Shores wrote:
> On Wednesday 29 March 2006 15:32, David Bateman wrote:
> > Anglade Pierre-Matthieu wrote:
> > >Hi all,
> > >
> > >I've some kind of very dumb problem with octave's synthax.
> > > probably because I don't mastered it at all I'm not able to
> > > solve the following problem:
> > >
> > >I have a function which look like having two variables but have
> > > in fact a single one and I can't find the way to tell this to
> > > octave. Here is the function (LateX form):
> > >f(x) = \int_a^b g(x,y) dy
> > >
> > >In order to compute that I first define g(x,y)
> > >Then I'd like to use the "quad" function to get the integral
> > > over the range o "y" values.
> > >but I d'ont find the way to tell quad that my function is now
> > > g(x,y) but with a fixed "x" value.
> > >
> > >Obviously I need to do this on the fly ( i.e. I can't define a
> > >function for each value of x) because otherwise it would take
> > > too long to get a complete plot...
> > >
> > >Could anybody kindly help me?
> > >
> > >
> > >--
> > >Pierre-Matthieu Anglade
> >
> > There is currently no way to do this, though funnily I just
> > implemented it with the attached patch I'm working on in another
> > thread about importing octave-forge changes into octave. So if
> > you want to rebuild octave the you have the patch :-)
> >
> > D.
> 
> True, you can't do it in a straightforward manner, but if you're 
> willing to live with globals, you can get this job done by creating 
> only one auxiliary wrapper function once and for all:
> 
> octave:2> global x
> octave:3> function retval = gx(y)
> > global x
> > retval = g(x,y);
> > end
> octave:4> % now make up any g(x,y) you want, but not anonymous
> octave:4> function retval = g(x,y)
> > retval = x.^2 +y.^2;
> > end
> octave:5> x = 1;
> octave:6> quad('gx',0,1)
> ans = 1.3333
> octave:7> x = 0;
> octave:8> quad('gx',0,1)
> ans = 0.33333
> 
> 
> 
> 
> 
> 
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Octave is freely available under the terms of the GNU GPL.

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