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## Accessing Arbitrary Dimensions

 From: Bill Denney Subject: Accessing Arbitrary Dimensions Date: Sun, 24 Feb 2008 22:09:34 -0500 User-agent: Thunderbird 2.0.0.9 (Windows/20071031)

```Hi,

```
I'm trying to run code where I don't know the dimension that I'm wanting to use a priori. In other words, I want to take as an input argument the dimension that I want to work on with a function that works similarly to max (hhigh.m, attached).
```
A similar example to what I want to do is:

function y = test(x, dim)
n = 5;
sz = size(x);
for i = 1:sz(dim)
## the next line should be corrected to
points = x(:,:,:,max(1,i-n+1),:,:)
y = max(x(points)
endfor

```
I had the idea to use sub2ind to compute all the points that I need to use, but I was wondering if there was a simpler (and possibly faster) way than something like this in the loop:
```
sz = size (x);
idx = max(1, i-n+1)
sz_tmp = mat2cell(ones (length (idx),1)*sz, 1, length (sz));
sz_nodim = sz;
sz_nodim(dim) = [];
points = zeros (length (idx), prod (sz_nodim));
for j = 1:length(idx)
sz_tmp2 = sz_tmp;
sz_tmp2{dim} = idx;
points(j,:) = sub2ind(sz, sz_tmp2{:});
endfor

```
All of the above was typed directly into this e-mail, and I'm pretty sure that it doesn't do quite what I'm wanting, but hopefully it gets the idea across.
```
Thanks,

Bill
```
```## Copyright (C) 2008 Bill Denney
##
## This software is free software; you can redistribute it and/or modify it
## the Free Software Foundation; either version 3 of the License, or (at
## your option) any later version.
##
## This software is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this software; see the file COPYING.  If not, see

## -*- texinfo -*-
## @deftypefn {Function File} {hhv} = hhigh (data)
## @deftypefnx {Function File} {hhv} = hhigh (data, nperiods)
## @deftypefnx {Function File} {hhv} = hhigh (data, nperiods, dim)
##
## Compute the highest high value of @var{data} for the past
## @var{nperiods} (default: 14) across the dimension, @var{dim}
## (default: 1).
##
## @seealso{llow}
## @end deftypefn

## Created: 24 Feb 2008

function hhv = hhigh (data, nperiods, dim)

if nargin < 1 || nargin > 3
print_usage ();
elseif ~ isvector (data)
## FIXME
error ("cannot yet handle more than one dimensional data")
endif
if nargin < 2
nperiods = 14;
endif
if nargin < 3
## Use the first non-singleton dimension
dim = find (size (data) > 1, 1);
endif

if dim > ndims (data)
error ("dim cannot be greater than the number of dimensions in data");
endif

sz = size (data);
hhv = data;
for i = 1:sz(dim)
hhv(i) = max (data(max (i-nperiods+1, 1):i));
endfor

endfunction

## Tests
%!shared c, h
%! c = [22.44 22.61 22.67 22.88 23.36 23.23 23.08 22.86 23.17 23.69 23.77 23.84
24.32 24.8 24.16 24.1 23.37 23.61 23.21 25];
%! h = [22.44 22.61 22.67 22.88 23.36 23.36 23.36 23.36 23.36 23.69 23.77 23.84
24.32 24.8 24.8 24.8 24.8 24.8 24.8 25];
%!assert(hhigh(c), h)
%!assert(hhigh(c'), h')
```