uniq -c

[John W. Eaton]

On 27-Aug-2004, Mike Miller <address@hidden> wrote:

| Is there a way to count repetitions of a value in a vector?  In unix/linux 
| we could use "uniq -c" to count consecutive identical lines.  Is there 
| something analogous in Octave?  If not, can one of you come up with a 
| clever scheme for doing this within Octave?  (I've been on this list long 
| enough to know that the answer is yes to that last question!)
| 
| I really just need the counts and not a list of the values being counted.
| Hmm... I just realized that if I had an ordinary 'uniq' function, I could 
| get the "uniq -c" this way (for column vector x):
| 
| [NN,XX] = hist(x,uniq(x))
| 
| Then [NN,XX] would be the "uniq -c" output and XX would actually equal 
| uniq(x).

Octave has

  create_set
  intersection
  union

Matlab appears to have

  unique
  union
  intersect
  setdiff
  setxor
  ismember

These names are also available in Octave-forge.  It looks like the
functions in Octave-forge would not need much work to be included in
the core Octave distribution.  I'm not sure what the differences are
between these:

  octave        octave-forge

  create_set    unique
  intersection  intersect
  union         union

but if possible, they should be merged so we only have one set of set
functions instead of two (the old Octave names could simply become
wrappers around the new compatible functions).

jwe



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