how can we estimate memory requirements for nchoosek?

>> help nchoosek
nchoosek Binomial coefficient or all combinations.
 ...
  nchoosek(V,K) where V is a vector of length N, produces a matrix
  with N!/K!(N-K)! rows and K columns.  Each row of the result has K of
  the elements in the vector V.  This syntax is only practical for
  situations where N is less than about 15.
 ...

TMW writes documentation for a reason...

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Andy 2018-8-4

编辑：dpb 2018-8-4

I like this answer: https://se.mathworks.com/matlabcentral/answers/93323-is-there-a-command-to-compress-a-matrix-in-memory-in-matlab

Nonetheless in our case there ARE many equal sequences of values so compression could make sense. But I don't see anything baked in that could do this, is it?

dpb 2018-8-4

编辑：dpb 2018-8-4

在 MATLAB Online 中打开

>> nchoosek(int16(1:5),3)
ans =
10×3 int16 matrix
...
>> whos ans
Name       Size            Bytes  Class    Attributes
ans       10x3                60  int16              
>> nchoosek((1:5),3)
ans =
...
>> whos ans
Name       Size            Bytes  Class     Attributes
ans       10x3               240  double  
>>

Is 4:1; uint8 would be 8:1 and handle values up to 255; as implemented it may require double() first I don't know and there's still the issue of the specific recursive algorithm used that probably could be improved on.

For the latter, as recommended earlier, see The Art of Computer Programming Vol 4 Generating All-tuples and Permutations

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