Combinations with a condition

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Nicolas Leport
Nicolas Leport 2023-2-9
评论： Nicolas Leport 2023-2-9
I am trying to create a matrix that list all combinations possible under a certain condition. Right now I am creating all combinations and then filtering but the matrix of combination is too large.
I want to keep only when
Thank you
I am putting an example with smaller vector size
x = [0 0.25 0.5 0.75 1]
x_1 = [0 0.5 1]
x_2 = [0 0.5 1]
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Jan
Jan 2023-2-9
I don't either. What are the inputs you want to combine?
Nicolas Leport
Nicolas Leport 2023-2-9
Sorry I wasn't clear
I want to have all to possible combinations of x, x_1 and x_2 with the condition
I want to end with something like this
Hope it makes more sense
0 0 0
0.25 0 0.5
0.25 0.5 0
0.5 0 1
0.5 0.5 0.5
0.5 1 0
0.75 0.5 1
0.75 1 0.5
1 1 1

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Voss
Voss 2023-2-9
Ran in:
Maybe something like this?
x = [0 0.25 0.5 0.75 1];
x_1 = [0 0.5 1];
x_2 = [0 0.5 1];
x_12 = (x_1.'+x_2)/2;
[ism,idx] = ismember(x_12,x);
[r,c] = find(ism);
result = [x_1(r); x_2(c); x(idx(ism))].'
result = 9×3
0 0 0 0.5000 0 0.2500 1.0000 0 0.5000 0 0.5000 0.2500 0.5000 0.5000 0.5000 1.0000 0.5000 0.7500 0 1.0000 0.5000 0.5000 1.0000 0.7500 1.0000 1.0000 1.0000
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Walter Roberson
Walter Roberson 2023-2-9
Voss's solution creates all combinations and filters them, which you had said gets too large for your purposes.
ismember with floating point is risky. This example with exact fractions of powers of 2 gets away with it, but you would have problems with 0.1 and 0.2 for example
Nicolas Leport
Nicolas Leport 2023-2-9
I actually changed x, x1, x2 to be whole number and then divide the result matrix by the number of data points. It works fine. But I don't know how to modify it to do it with x, x1, x2 and x3

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