How to generate a random number of n bits length?

Let's say a function takes input n as the bit length and outputs a random number. For example, for n = 4, the output range is [0 - 15] which also includes the range for n = 3 i.e. [0 - 7]. The function should generate the number in the range [8 - 15] and not in the range [0 - 15]. How to do this and how to generalize it for any n?

[KALYAN ACHARJYA]

The function should generate the number in the range [8 - 15] and not in the range [0 - 15]. How to do this and how to generalize it for any n?

Can you clarify this statement? if n=3 then ??

What I am getting you want three-bit representation(when n=3) in the range [8 - 15]??

[Mohsin Shah]

For n = 3 then the output range is [0-7] which includes the range [0-3] which is for n = 2

[KALYAN ACHARJYA]

@Mohsin Check my answer, as per your requirement? If any modification required, let me know.

Answer 1

[Guillaume]

For n = 4 it should generate a number in the range [8-15]

If I understand correctly, you want a 4 bit random number with the MSB always set to 1. That sounds like a strange requirement, probably not thought properly, but this is simply equivalent to generating a 3 bit random number and tacking 1 as the MSB. The generic version of that (generating a n-1 bit number + MSB of 1) is:

n = 4
number = randi([1, 2^(n-1)]) + 2^(n-1) - 1

[Mohsin Shah]

It worked for me. Thank you.

[ANz Eisenheim]

I want generate a random large sequence of bits and block the sequence. each block of data consisting of 4 bits. Can Anyone help?

[John D'Errico]

@ANz Eisenheim - please don't revive dead questions with a new question. If you have a new question, then ask it separately.

Regardless, what is the problem? Generate random bits as a vector. rand can do it. randi can do it. As long as the sequence is of a length that is a multiple of 4, you are done. So WTP?

Answer 2

[KALYAN ACHARJYA]

function bit_result=rand_bits(n)
result=randi([2^(n-1), 2^n]);
bit_result=de2bi(result,n)
end

[Mohsin Shah]

For n = 4, it generates a number in the range [0-7] which is not required. For n = 4 it should generate a number in the range [8-15].

[KALYAN ACHARJYA]

@Mohsin I have edited the answer, can you verify it?

[Mohsin Shah]

I appreciate your efforts but the edited function still doesn't work. Check the answer of Guillaume which worked for me.