Re: ode45 inclusion into core

[Carlo De Falco]

On 6 Oct 2015, at 09:44, Richard Crozier <address@hidden> wrote:

> There is an undocumented feature of matlab's ode45 and most of the other ode* 
> functions. They pass any additional arguments to ode45 after the 'options' 
> arguments to the ode evaluation function, crossing detection function and 
> output function. This is really useful and would be nice to have in Octave's 
> versions too if it's not present.

This feature is present in the current version of ode45 in Octave, but I think 
it was deprecated in Matlab.
The recommended way of achieving the same result is via a anonymous function, 
i.e., supposing you have

function r = resfun (t, y, z)
  r = t + y + z;
endfunction

instead of using the deprecated approach of passing the extra parameter z as an 
additional input to de45:

  ode45 (@resfun, tspan, y0, options, z)

you use an anonymous function to bind the value of z

  ode45 (@(t, y) resfun(t, y, z), tspan, y0, options)

this techinique is reccomended in Matlab [1, 2], but the old behaviour, now 
deprecated and undocumented, is still
working and I think is kept for bacward compatibility.

In the Octave implementation I was considering removing this feature as it make 
the code much more complicated.


> Richard


c.


[1] http://it.mathworks.com/help/matlab/ref/ode45.html "Parameterizing 
Functions explains how to provide additional parameters to the function fun, if 
necessary."
[2] http://it.mathworks.com/help/matlab/math/parameterizing-functions.html