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The usage of DuplicateFreeQ

Hongyi Zhao
Posted 2 years ago

See my following example:

In[347]:= x=Tuples[{0,1},3]
Select[x,! #[[1]]==#[[2]]==#[[3]]&]
Select[x,DuplicateFreeQ]

Out[347]= {{0, 0, 0}, {0, 0, 1}, {0, 1, 0}, {0, 1, 1}, {1, 0, 0}, {1, 
  0, 1}, {1, 1, 0}, {1, 1, 1}}

Out[348]= {{0, 0, 1}, {0, 1, 0}, {0, 1, 1}, {1, 0, 0}, {1, 0, 1}, {1, 
  1, 0}}

Out[349]= {}

I want to obtain the similar result as the second command by using the DuplicateFreeQ in the last command shown above. Why doesn't my usage return any results?

Regards,
Zhao
POSTED BY: Hongyi Zhao
2 Replies
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Hongyi Zhao
Hongyi Zhao
Posted 2 years ago

Nice. It does the trick:

In[12]:= xx=Tuples[{0,1},3]
Select[xx,! #[[1]]==#[[2]]==#[[3]]&]
%==Select[xx, ! SameQ @@ # &]==Select[xx, ! Equal @@ # &]

Out[12]= {{0, 0, 0}, {0, 0, 1}, {0, 1, 0}, {0, 1, 1}, {1, 0, 0}, {1, 
  0, 1}, {1, 1, 0}, {1, 1, 1}}

Out[13]= {{0, 0, 1}, {0, 1, 0}, {0, 1, 1}, {1, 0, 0}, {1, 0, 1}, {1, 
  1, 0}}

Out[14]= True

P.S. It seems that in this case, both SameQ and Equal work.
POSTED BY: Hongyi Zhao
Hans Milton
Hans Milton
Posted 2 years ago

Why doesn't my usage return any results?

That is because all matrix rows contains duplicates.

SameQ could be used:

Select[x, ! SameQ @@ # &]
POSTED BY: Hans Milton
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