Swap characters in sequence randomly (Matlab)

Question

I have an input value is a set of sequences as follows:

{ 'ABCDE'
  'ABCD'
  'ABE'
  'ABCDE'
  'ABD'
  'ABCD'
  'ABCDE' }

I try to swap 'A' and 'B' in 3 random sequences and keep other sequences no changes. Could anyone have any suggestion ?

Answer 1

A possible solution

A={ 'ABCDE'
  'ABCD'
  'ABE'
  'ABCDE'
  'ABD'
  'ABCD'
  'ABCDE' };

N = numel(A);

for r = randperm(N,3)
    A(r) = A{r}([2 1 3:end]);
end

or

for r = randperm(N,3)
    A{r}(1:2) = A{r}([2 1]);
end

randperm(N,3) selects 3 random values from 1:N

then with indexing [2 1 3:end] we can swap first and second elements

Answer 2

If you do not want to have a for loop but instead have an extra data conversion step from cell to char and then from char back to cell, this would solve your problem:

N = numel(A);
r = randperm(N,3);
A = char(A);
A(r,[1,2]) = A(r,[2,1]);
A = cellstr(A);