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Generate 0 and 1

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Ronak Sakaria
Ronak Sakaria il 9 Mag 2012
Commentato: Walter Roberson il 22 Mar 2022
Hi,
How to generate 0 and 1 with equal probability?
I wanna generate sequence like 010101 or 011001 i.e probability of 0 and 1 should be 0.5.
  3 Commenti
James Tursa
James Tursa il 8 Ago 2018
This is sufficiently different from the original question that I would advise you delete this comment and instead post it as a new Question.
Srik G
Srik G il 27 Gen 2022
I wanna generate sequence like 010101 or 011001 with some sampling time in matlab- simulink blocks. Please suggest the block which can do this job in simulink ?

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Risposta accettata

Walter Roberson
Walter Roberson il 9 Mag 2012
round(rand)
or
rand >= 0.5
  4 Commenti
Katyayani Modi
Katyayani Modi il 23 Set 2017
He i have one question I want to generate 1's or 0's but 1's will occur 70% of the time with round, ceil, fix, floor function.
Image Analyst
Image Analyst il 23 Set 2017
To get a specified percentage of 1's, try this:
numberOfElements = 1000; % Whatever.
percentageOfOnes = 70; % Whatever.
numberOfOnes = round(numberOfElements * percentageOfOnes / 100)
% Make initial signal with proper number of 0's and 1's.
signal = [ones(1, numberOfOnes), zeros(1, numberOfElements - numberOfOnes)];
% Scramble them up with randperm
signal = signal(randperm(length(signal)));
% Count them just to prove it
numOnes = sum(signal)

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Più risposte (8)

Image Analyst
Image Analyst il 9 Mag 2012
Ronak, This will do the trick:
n = 10; % Total length must be even to have even # of 0s and 1s.
numberOfOnes = n/2
% Get a list of random locations, with no number repeating.
indexes = randperm(n)
% Start off with all zeros.
x = zeros(1, n);
% Now make half of them, in random locations, a 1.
x(indexes(1:numberOfOnes)) = 1

Geoff
Geoff il 9 Mag 2012
I wouldn't do this using the double version of rand. While it's not really incorrect to use rand for this, I would use randi instead. Integers are the native data type for random number generation.
This generates an m-by-n matrix of zeros and ones:
x = randi(2,m,n) - 1
There is still a chance, however, that when generating six random numbers they will be all 1, all 0, or anything else where the distribution is not perfect. If you require an equal number of ones and zeros, but scrambled, you could do this:
% By definition, we require an EVEN number for N
N = 6;
x = repmat([0 1], 1, N/2);
% Randomly switch two individual numbers N times.
for t = randi(N, 2, N)
x(t) = x(t([2 1]));
end
[edited: made swap code less C-like]
  5 Commenti
Walter Roberson
Walter Roberson il 9 Mag 2012
Integers are (nearly always) what underlies uniform random generators. However, other distributions such as rand() may use other methods.
MATLAB does not expose the 32 bit integer generation capability of the Twister algorithm. If I recall, it uses two Twister calls to generate the 53 bit double in rand().
I do not have access to randi() to check, but because it needs to be uniform random over a variable range of integer values (rather than always over a power of 2), fairness considerations usually make it easier to use a double and multiply by the span.
Walter Roberson
Walter Roberson il 16 Mag 2012
I meant to write that randn() may use other methods.

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Narayan Chaudhary
Narayan Chaudhary il 16 Mag 2012
randerr(1,6,[0 3;0 1])
1x6 matrix with 0 and three non-zero entries with probability of 3 non zero entries being 1 i.e. 0,5 in overall matrix
  1 Commento
juan camilo lores acosta
juan camilo lores acosta il 18 Mar 2020
muchas gracias salvaste una vida :)

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Haoming Mai
Haoming Mai il 24 Feb 2018
Hi
How to generate 0 and 1 with probability of 1/3?
  1 Commento
Image Analyst
Image Analyst il 24 Feb 2018
Modificato: Image Analyst il 24 Feb 2018
With randperm
total = 99
numOnes = round(total/3)
r = zeros(1, total); % All zeros to start.
% Now assign a third of them to 1
indexes = randperm(total, numOnes);
r(indexes) = 1
sum(r) % Check to make sure. Should be 33

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Walter Roberson
Walter Roberson il 24 Feb 2018
Modificato: James Tursa il 8 Ago 2018
A few years after this question was posted, I posted
In which I proved that it is not possible to generate 0 and 1 with exactly equal probability with any of the MATLAB random number generators.

Akira Agata
Akira Agata il 18 Mar 2020
Just FYI:
To evaluate BER (Bit Error Rate) of digital communication system, PRBS (Pseudo Random Binary Sequence) has been commonly used as a test pattern for many years. Since PRBS sequence with length of bits always contains specific number of 1s and 0s (more precisely, 1s and 0s ), maybe you can use this for your purpose.
% For example, the following code generates PRBS sequence of r=4 (15bit length)
pnSequence = comm.PNSequence(...
'Polynomial', [4 3 0],...
'InitialConditions',[0 0 0 1],...
'SamplesPerFrame', 15)
prbsSequence = pnSequence();

Prakash Reddy Pasham
Prakash Reddy Pasham il 3 Gen 2022
I just need the 1D array of zeros and Ones with our required probability of ones.
  1 Commento
Walter Roberson
Walter Roberson il 3 Gen 2022
https://www.mathworks.com/matlabcentral/answers/37827-generate-0-and-1#comment_538887 shows how to achieve a specific density of ones -- for example, exactly 33 ones out of 99.
Note that this is not the same as the probability being 33/99 = 1/3 : probability is statistical. For example,
simulations = mean(rand(1000,1000) <= 1/3,1);
min(simulations), max(simulations)
ans = 0.2840
ans = 0.3870
histogram(simulations)

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Omair Mohammad Ikram
Omair Mohammad Ikram il 22 Mar 2022
Modificato: Image Analyst il 22 Mar 2022
What is the code for generation of a random sequence of bits with a specified probability of p0 of the bit 0?
  3 Commenti
Omair Mohammad Ikram
Omair Mohammad Ikram il 22 Mar 2022
Thanks alot
Walter Roberson
Walter Roberson il 22 Mar 2022
Do you need probability or do you need a specific number of values in a state? If you need exactly floor(p0*samples) then use randperm like above. If you want probability then
out = rand(1,samples) > p0;
for probability p0 of a 0.
More common would be to specify the probability of a 1, in which case you would typically use <.

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