Squeeze works differently in Matlab

[John W. Eaton]

On  2-Jul-2004, Andy Adler <address@hidden> wrote:

| I'm trying to get some code to run under Matlab and Octave,
| and I note that 'squeeze' works differently, if there is only
| one non-singleton dimention:
| 
| Matlab:
|     >> squeeze(rand(2,1,3))
|     ans =
|         0.4447    0.7919    0.7382
|         0.6154    0.9218    0.1763
| 
|     >> squeeze(rand(1,1,3))
|     ans =
|         0.4057
|         0.9355
|         0.9169
| 
| Octave (2.1.57 - today's CVS):
|     octave:1> squeeze(rand(2,1,3)) # This is OK
|     ans =
|       0.47701  0.72476  0.80614
|       0.64084  0.87862  0.71905
| 
|     octave:2> squeeze(rand(1,1,3)) # This is transposed wrt Matlab
|     ans =
|       0.839686  0.112393  0.016944

I also see that squeeze has no effect on 2-d arrays so that squeezing
a row vector does not convert it to a column vector.  Hmm.  So to be
contemptible, the algorithm should really be

  if (ndims > 2)
    remove all singleton dimensions;
    if (ndims == 0)
      dims = [1, 1];
    elseif (ndims () == 1)
      dims = [dims, 1];
    endif
  endif

?  Would this produce the desired results in all cases?  If so, then
please try the following patch.

Thanks,

jwe


liboctave/ChangeLog:

2004-08-03  John W. Eaton  <address@hidden>

        * Array.cc (Array<T>::squeeze): Do nothing for 2-d arrays.  For
        arrays with more than two dimensions and only one non-singleton
        dimension, return a column vector.


Index: liboctave/Array.cc
===================================================================
RCS file: /usr/local/cvsroot/octave/liboctave/Array.cc,v
retrieving revision 1.119
diff -u -r1.119 Array.cc
--- a/liboctave/Array.cc        26 Jul 2004 14:37:05 -0000      1.119
+++ b/liboctave/Array.cc        3 Aug 2004 19:56:00 -0000
@@ -71,50 +71,45 @@
 {
   Array<T> retval = *this;
 
-  bool dims_changed = false;
+  if (ndims () > 2)
+    {
+      bool dims_changed = false;
 
-  dim_vector new_dimensions = dimensions;
+      dim_vector new_dimensions = dimensions;
 
-  int k = 0;
+      int k = 0;
 
-  for (int i = 0; i < ndims (); i++)
-    {
-      if (dimensions(i) == 1)
-       dims_changed = true;
-      else
-       new_dimensions(k++) = dimensions(i);
-    }
+      for (int i = 0; i < ndims (); i++)
+       {
+         if (dimensions(i) == 1)
+           dims_changed = true;
+         else
+           new_dimensions(k++) = dimensions(i);
+       }
 
-  if (dims_changed)
-    {
-      switch (k)
+      if (dims_changed)
        {
-       case 0:
-         new_dimensions = dim_vector (1, 1);
-         break;
+         switch (k)
+           {
+           case 0:
+             new_dimensions = dim_vector (1, 1);
+             break;
 
-       case 1:
-         {
-           int tmp = new_dimensions(0);
+           case 1:
+             {
+               int tmp = new_dimensions(0);
 
-           new_dimensions.resize (2);
+               new_dimensions.resize (2);
 
-           if (dimensions(0) == 1)
-             {
-               new_dimensions(0) = 1;
-               new_dimensions(1) = tmp;
-             }
-           else
-             {
                new_dimensions(0) = tmp;
                new_dimensions(1) = 1;
              }
-         }
-         break;
+             break;
 
-       default:
-         new_dimensions.resize (k);
-         break;
+           default:
+             new_dimensions.resize (k);
+             break;
+           }
        }
 
       retval.make_unique ();