A better way to act on a dim of an N-d array?

[Ben Abbott]

On Feb 1, 2008, at 2:27 AM, John W. Eaton wrote:

> On 31-Jan-2008, Ben Abbott wrote:
>
> |
> | On Jan 29, 2008, at 10:35 PM, Ben Abbott wrote:
> |
> | >
> | > On Jan 29, 2008, at 8:30 PM, Ben Abbott wrote:
> | >
> | >> While working on quantile and prctile functions for Octave, I  
> am in
> | >> need to functionally operate on the dim-th dimension of a N-d  
> array.
> |
> | What I'm looking to do is allow a specific dimension of an N-d array
> | to be acted upon by a function that returns a vector of a consistent
> | length.
> |
> | The algirithms for calculating the quanitles of a sample are
> | sufficiently varied that the methods used by mean(), median(),  
> etc, to
> | support N-d arrays, are insufficient for my application.
> |
> | As I am not a competent c/c++ programmer, I chose to do the job in  
> an
> | m-file ... but is there a better way to do this?
>
> I'm not sure, but it does seem fairly complex.  But if it is necessary
> to use your dimfunc, then you should probably use
>
>  function y = dimfunc (func, x, dim, varargin)
>
> instead of
>
>  function y = dimfunc (func, x, dim, arg1, arg2, arg3, arg4, arg5)
>
> so that dimfunc can handle any number of additional arguments, not
> just 5, and so you can replace
>
>    if (nargin == 3)
>      temp = func (xdim(:));
>    elseif (nargin == 4)
>      temp = func (xdim(:), arg1);
>    elseif (nargin == 5)
>      temp = func (xdim(:), arg1, arg2);
>    elseif (nargin == 6)
>      temp = func (xdim(:), arg1, arg2, arg3);
>    elseif (nargin == 7)
>      temp = func (xdim(:), arg1, arg2, arg3, arg4);
>    elseif (nargin == 8)
>      temp = func (xdim(:), arg1, arg2, arg3, arg4, arg5);
>    endif
>
> with
>
>   temp = func (xdim(:), varargin{:});
>
> jwe

Thanks for the tip.

I'll make the change and post the patch on the other thread.

Ben