Random number generation problem

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Hello everyone, i am generating random channel assignment using randperm in the following code. Since the number of users are greater than the number of channels, so there will be a repetition of channel assignment. My question is how can i generate a random number from a given range [1-10], if the generated number for example is channel 9 and if that number 9 channel is unavailable then i want to generate another number between [1-10] but this time excluding number 9 channel. and this process continue until i get a free channel number from [1-10]
channels = 10;
users = 100;
challocation = ceil(channels*(randperm(users)/users));

Accepted Answer

Star Strider
Star Strider on 12 Sep 2014
Edited: Star Strider on 12 Sep 2014
Use the setdiff function to find the available channels, then randperm on the result.
  6 Comments
Aftab Ahmed Khan
Aftab Ahmed Khan on 12 Sep 2014
Yes, it works exactly. Thanks dear.

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More Answers (1)

Roger Stafford
Roger Stafford on 12 Sep 2014
You say "the number of users are greater than the number of channels, so there will be a repetition of channel assignment" . In that case just use 'randperm' multiple times. Let n = number of channels and m = number of users.
q = ceil(m/n);
C = zeros(q*n,1);
for k = 0:q-1
C(k*n+1:k*n+n) = randperm(n);
end
C = C(1:m); % <-- These are the channels nos. assigned to the m users
The number of users assigned to any channel will never exceed the number of users assigned to another other channel by more than one and yet the assignments are random.

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