How to create N-tuples in Matlab?

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Pontus Vikstål
Pontus Vikstål 2018-9-29
回答： Steven Lord 2024-1-5
What would be the easiest way to create a list of n-tuples in Matlab?
For example, if I want to generate all possible 3-tuples of 0 and 1: I'd want to generate the following set of tuples:
((0,0,0),(0,0,1),(0,1,0),(0,1,1),(1,0,0),(1,0,1),(1,1,0),(1,1,1))

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采纳的回答

Bruno Luong
Bruno Luong 2018-9-29
dec2bin(0:2^3-1)-'0'
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Walter Roberson
Walter Roberson 2021-9-30
Ran in:
A = dec2bin(0:2^3-1)
A = 8×3 char array
'000' '001' '010' '011' '100' '101' '110' '111'
dec2bin() outputs characters.
double(A)
ans = 8×3
48 48 48 48 48 49 48 49 48 48 49 49 49 48 48 49 48 49 49 49 48 49 49 49
Those characters have internal codes 48 ('0') or 49 ('1')
B = '0'
B = '0'
double(B)
ans = 48
The character code for '0' is 48
A - B
ans = 8×3
0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1
subtract the character code for '0' from the character codes for the bits to get relative offsets compared to '0' . Characters that were '0', upon having '0' subtracted, give a result of (numeric) 0 . Characters that were '1', upon having '1' subtracted, give a result of (numeric) 1 because the internal code for the character '1' is (numeric) 1 greater than the internal code for the character '0'
So subtracting '0 converts between characters '0' and '1' to numeric 0 and 1.

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更多回答（2 个）

Steven Lord
Steven Lord 2024-1-5
Ran in:
If you're using release R2023a or later of MATLAB you could use the combinations function to do this.
v = [0 1];
c = combinations(v, v, v)
c = 8×3 table
v v_1 v_2 _ ___ ___ 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1
If you need the result as a numeric array rather than a table array:
c = combinations(v, v, v).Variables
c = 8×3
0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1
Stephan Reichelt
Stephan Reichelt 2024-1-5
Ran in:
There is another quite simple implementation of this problem:
% define the values
v = [0, 1]
v = 1×2
0 1
% generate all combinations of length 3 with repetitions
C = combvec(v,v,v)'
C = 8×3
0 0 0 1 0 0 0 1 0 1 1 0 0 0 1 1 0 1 0 1 1 1 1 1
  1 个评论
John D'Errico
John D'Errico 2024-1-5
Ran in:
Note that combvec is not found in MATLAB, unless you have the neural net toolbox.
which combvec -all
/MATLAB/toolbox/nnet/nnet/nndatafun/combvec.m
help combvec
COMBVEC Create all combinations of vectors. combvec(A1,A2,...) takes any number of inputs A, where each Ai has Ni columns, and return a matrix of (N1*N2*...) column vectors, where the columns consist of all combinations found by combining one column vector from each Ai. For instance, here the four combinations of two 2-column matrices are found. a1 = [1 2 3; 4 5 6]; a2 = [7 8; 9 10]; a3 = combvec(a1,a2) Documentation for combvec doc combvec

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