Randomly return of a vector element. How to?

Hi everyone,

I have a vector A, of let's say, 30 elements.

I need Matlab (R2017b) to return the same element constantly and at random times return one of the rest elements, randomly chosen.

How can I do such a thing?

[Adam]

doc randi

[Dennis]

You can use randi to generate a random integer. You can use it as index or as probability.

 A=1:30;
  for i=1:1000
      prob = randi(10);
      if prob == 1         %1 in 10 chance
          rdm_el=randi(numel(A));
          value= A(rdm_el);
      else
          value=1;
      end
  end

[Tasos Ampelas]

Thank you Dennis.

The ''if prob == 1'' gives the chance of the random pick right?

So if I write ''if prob == 2,5'' this will be 1 random pick in 4?

[Dennis]

randi only provides natural numbers (1,2,3,4). If you want a chance of 1 in 4 change the line above to

prob = randi(4);

short explanation:

prob = randi(4); %creates a random integer between 1 and 4 (1,2,3 or 4)
if prob ==1      % checks if the random integer is 1

Answer 1

[dpb]

ixFix = N;                          % set the particular element however is to be done...
iRet=[ixFix randperm(numel(A),1)];  % index vector of positions to return
B=A(iRet);                          % and get them...

Can, of course, eliminate temporaries shown for clarity if not needed for other purposes in the application.

B=A([N randperm(numel(A),1)]);