Random combinations of symbols (restored)

Matt J undeleted this a 3rd time: (I won't stop)

probVector = [0.4   0.05    0.2    0.15    0.2]; 
P(A)= 0.4 P(B)=0.05 P(C)=0.2 P(D)=0.15 P(E)=0.2

function b = GenerateInputSymbols(N, probVector)          
        %This function generates a random vector of N characters according the probability mass function specified in probVector.
        %Each character is generated independently of all the others.
        %Use the rand function (or functions related to rand in MATLAB) in order generate a realization of such a random vector of N characters.
end

For Example;

N=3;
Output= [0.05 0.15 0.4]

How we can generate this function? We want that from probvectors values and porbability of Letters A B C D E , as a result of this function we want to see AEBCD or BDCEA... randomly one of them. PS: It has to return values as related with their probabilities. For example in 100 trials there would 40 A's 5 B's 20 C'S ....

[Guillaume]

Judging from the comment in the function prototype, this looks like homework.

So, what specific problem are you encountering? We don't mind helping if you've got a specific problem but we don't like doing your homework for you.

[Jan]

"Output= [0.05 0.15 0.4]" looks strange. Later on you explain, that the result should be 'AEBCD'.

[Matt J]

Dogukan Kara's post (backup copy):

probVector = [0.4   0.05    0.2    0.15    0.2]; 
P(A)= 0.4 P(B)=0.05 P(C)=0.2 P(D)=0.15 P(E)=0.2

function b = GenerateInputSymbols(N, probVector)          
        %This function generates a random vector of N characters according the probability mass function specified in probVector.
        %Each character is generated independently of all the others.
        %Use the rand function (or functions related to rand in MATLAB) in order generate a realization of such a random vector of N characters.
end

For Example;

N=3;
Output= [0.05 0.15 0.4]

How we can generate this function? We want that from probvectors values and porbability of Letters A B C D E , as a result of this function we want to see AEBCD or BDCEA... randomly one of them. PS: It has to return values as related with their probabilities. For example in 100 trials there would 40 A's 5 B's 20 C'S ....

[Jan]

@Matt J: Isn't this the text as it is found in the question currently?

[Matt J]

@Jan: Yes, but it may not remain that way if the posts below are any indication,

https://www.mathworks.com/matlabcentral/answers/374037-a-a-a-a-a-a-a-a-a

https://www.mathworks.com/matlabcentral/answers/372319-a-a-a-a-a

https://www.mathworks.com/matlabcentral/answers/372187-sum-of-each-row

[Matt J]

And, in fact, Dogukan Kara just now tried to delete this question, too. [sigh]

[Guillaume]

"I have all the copyrights of this question and do not give permission to edit"

As per the terms of use you agreed to when you created you account: You agree that all Content that you contribute to the MATLAB Answers portion of MATLAB Central will be licensed under the Creative Commons Attribution Share Alike 3.0 license. Which means that you agreed that any post could be edited and you cannot revoke this permission.

[Jan]

Thanks Guillaume and Matt J for caring about this thread.

Answer 1

[Jan]

If you have the symbols and probabilities

symbols = 'ABCDE'
prob    = [0.4, 0.05, 0.2, 0.15, 0.2];

You can get one symbol with its probability using:

probAccum      = cumsum(prob);
probAccum(end) = 1.0;  % Care for rounding errors
index          = find(rand >= probAccum, 1);

Now the chance to get index=2 is 4 times higher than index=3.

I leave the implementation for multiple N and creating the function up to you, because this looks like a homework question.

See histcounts for another approach.

Answer 2

[Jos (10584)]

A perfect job for my old RANDP function that picks random values using probabilities :)

Objects    = 'ABCDEF'
probVector = [0.4 0.05 0.2 0.15 0.2]; 
N = 10 ;

idx = randp(probVector, 1, N)
List = Objects(idx)

RANDP can be downloaded from the File Exchange: https://uk.mathworks.com/matlabcentral/fileexchange/8891-randp