How to generate a a restricted binary number

Dear friends

I would like to generate a random number include 24 bits 4 bits of 1 and 20 bits of 0. Can you help me?

Best Regards

Mohsen

Answer 1

[Jan]

What exactly is a "number include 24 bits"?

This sets 4 elements to 1 and 20 to 0:

v = zeros(1, 24);
v(randperm(24, 4)) = 1;

What is the wanted output?

result = bin2dec('0' + v)
% or
result = v * power(2, 0:23).'

Instead of creating the sum using the dot product, you can use the indices replied by randperm directly:

result = sum(2 .^ (randperm(24, 4) - 1));

I hope this was not a homework question. Otherwise it will be hard for you to submit your own solution now. But you participate in this forum for 6 years now, such that I assume that you are not in the learning phase anymore.

Answer 2

[Mohsen]

Exuce me,

There is a problem. In fact, i have a optimization algorithm and the input dimention and max and min. must be determined.

a posible state can be:

[0 1 0 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0]

or

[0 0 0 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0]

or...

there are four swing "1"s in this vector and total states is equal 10626(=). the vector length is 24. How do i define number dimention, max and min to derive this array?

[Jan]

I do not understand what "number dimension, max and min" means. Maximum and minimum of what? My answer includes a method to create random vectors already:

v = zeros(1, 24);
v(randperm(24, 4)) = 1;

Do you now want to create all these vectors? Then:

M = nchoosek(1:24, 4);
for k = 1:size(M, 1)
    v = zeros(1, 24);
    v(M(k, :)) = 1;
    ...
end

[Mohsen]

I get a new idea by your post.

Thank you very much