Finding index in a set

Hello. I have these two sets.

x1 = [0 , 0, 1, 0]

x2 = [0, 0, 0, 0]

I want to randomly generate one in x2 except the index 3, where the vaule is x1. The output will be look like:

x1 = [0, 0, 1, 0]

x2 = [1, 0, 0, 0] or [0, 1, 0, 0] or [0, 0, 0, 1].

How can I do that?

Answer 1

[Stephen23]

Simple and efficient:

x1 = [0,0,1,0];
x2 = [0,0,0,0];
ix = find(~x1);
iy = randi(nnz(ix),1);
x2(ix(iy)) = 1

x2 = 1×4

0 0 0 1

[Stephen23]

Lets try it in a loop:

for k = 1:64
    x1 = [0,0,1,0];
    x2 = [0,0,0,0];
    ix = find(~x1);
    iy = randi(nnz(ix),1);
    x2(ix(iy)) = 1
end

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

0 1 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

1 0 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

1 0 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 1 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

0 1 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

1 0 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 1 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 1 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

1 0 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

1 0 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

1 0 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

1 0 0 0

x2 = 1×4

0 0 0 1

x2 = 1×4

0 0 0 1

x2 = 1×4

1 0 0 0

x2 = 1×4

0 1 0 0

x2 = 1×4

1 0 0 0

Answer 2

[Arif Hoq]

one approach:

x1 = [0 , 0, 1, 0];
x2 = [0, 0, 0, 0];
% [value I]=find(x1==1);
b=perms(x1);
[row,col,v] = find(b(:,3));
b(row,:)=[];
c=b;
output=unique(c,'rows','stable')

output = 3×4

0 1 0 0 0 0 0 1 1 0 0 0

[Md. Nazrul Islam Siddique]

I want only one input. Everytime I run, I want to generate different x2 values. x1 values can be 1 at any position, not only 3.

[Md. Nazrul Islam Siddique]

Also, using perms I am getting same combination more than once.

[Arif Hoq]

I am confused. you can make x2 in sveral ways.

x1 = [0 , 0, 1, 0];
x2=circshift(x1,1,2)

x2 = 1×4

0 0 0 1

x3=circshift(x1,2,2)

x3 = 1×4

1 0 0 0

x4=circshift(x1,3,2)

x4 = 1×4

0 1 0 0

[Arif Hoq]

or using a function

x=4;
shiftv=2;
output=binvector(x,shiftv)

output = 1×4

0 1 0 0

function y=binvector(x,shiftv) 
 y=zeros(1,x);
 y(shiftv)=1;
end