Min/Max selection

That's look interesting.
How can I compile it?
When i try to install it with "minmax_install" i get the following error: "getmexopts [Bruno]: cannot open comopts.bat file".
How does this file have to look like?

thx
marcello

Thanks! It is very useful!

Thanks! Efficient (see note), really tricky+fast usage of shared values for columns accessing, sophisticated sorting, good documentation and an installation method, which considers different Matlab versions. Excellent for teaching using shared data copies in Mex files!

Although this function is not designed to work on small arrays, for this case the VARARGIN/VARARGOUT overhead might be avoidable. E.g. MINK:
  function varargout=mink(varargin)
  nout = cell(1, max(1, nargout));
  [nout{:}] = minmaxk(@minkmex, varargin{:});
  vargargout=nout;
10% faster for MINK(1:100, 10):
  function [V, Idx] = mink(list, k)
  if nargin == 1, k = 1; end
  if nargout == 2,
    [V, Idx] = minmaxk(@minkmex, list, k);
  else, V = minmaxk(@minkmex, list, k);
  end
For large inputs, this is obviously negligible. But there are no drawbacks.

NOTE: I've compared this with dull brute force search of the K.th smallest/largest elements. I'll send you the source by mail and be glad for your comments.

I have observed the following SERIOUS bug:

>> x=sparse([1 100 150 900 15000],1,[.4992 .4 0 0 .001],30e3,1,5);
>> maxk(x)
ans =
  3.8063e+295
>> [a I]=maxk(x)
a =
    0.4992
I =
     1

Joschua, thanks for the report. I have correct the code and hopefully it resolves these two issues.

I tried to install it on MATLAB 7.11.0 (R2010b), and got errors:
>> minmax_install
??? Error using ==> buildInternal_mxArrayDef at 35
Cannot parse matrix.h file

Error in ==> minmax_install at 25
buildInternal_mxArrayDef('Internal_mxArray.h');

Any ideas to fix this?
 

I'm afraid manually compiling won't work. Because Internal_mxArray.h is need for compiling. But this file is generated by buildInternal_mxArrayDef which will fail to run under R2010b since parsing matrix.h fails. :-(

Great! It works now. Thank you:)

I try minmax_install in a server without root account and get this error:

    mex: inplacecolumnmex.c not a normal file or does not exist.

??? Error using ==> mex at 218
Unable to complete successfully.

Error in ==> minmax_install at 28
mex(mexopts{:},'inplacecolumnmex.c');

What does it mean and what can I do? Matlab details are:
Version 7.8.0.347 (R2009a) 64-bit (glnxa64)

hi
first of all, i really appreciate your work. as it seems, it is very efficient.

but the problem is i still cant run it, although i used your fixed version for v2010b.
i used testminmax.m

here is what i get:

??? Error using ==> buildInternal_mxArrayDef at 35
Cannot parse matrix.h file

Error in ==> minmax_install at 25
buildInternal_mxArrayDef('Internal_mxArray.h');

Error in ==> testminmax at 11
    minmax_install();

Hi
i cant use this interesting code. when i run minimax_install, the following error appear:
Error: 'inplacecolumnmex.c' not found.
 
??? Error using ==> mex at 207
Unable to complete successfully.

Error in ==> minmax_install at 28
mex(mexopts{:},'inplacecolumnmex.c');
please help me
thanks

Hi
I try to compile(by GCC under Linux) minkmex.c/maxkmex.c, and encounter an error like

I did not figure out how to modify your C source file to fix the problem. I think your C implementation should be cross-platform.

minkmex.c: In function ‘MinMaxResult’:
minkmex.c:293:5: warning: incompatible implicit declaration of built-in function ‘memset’
minkmex.c: In function ‘LocResult’:
minkmex.c:322:5: warning: incompatible implicit declaration of built-in function ‘memset’
minkmex.c: In function ‘mexFunction’:
minkmex.c:544:25: error: expected expression before ‘/’ token

    mex: compile of ' "minkmex.c"' failed.