Creating all possible combination of a letter/string

dem_a='ABC'; % assume starting string is all upper
n = numel(dem_a);
result = repmat(dem_a,2^n,1);
mask = dec2bin((0:(2^n-1))') == '1';
result(mask) = result(mask) + ('a'-'A');

or that last line could be

result(mask) = lower(result(mask));

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Rahul J Hirur 2020-6-18

Thank you.

One tiny thing though,

dem_a if it has lowercase letter. It will throw some garbage in.

It can be solved using upper() function

James Tursa 2020-6-18

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Yes, e.g.,

result = repmat(upper(dem_a),2^n,1);

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Answer 2

Cris LaPierre 2020-6-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/550077-creating-all-possible-combination-of-a-letter-string#answer_452748

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There is no built-in function for this, but you can use the capabilitied of MATLAB to find the answer. Here's one way.

t = 'ABCabc';
% All possible permutations
p = perms(t);
% Only keep the unique combinations of the first 3 letters
p = unique(p(:,1:3),'rows')
% Only keep those permutations that have 'A' in the first column, 'B' in the 2nd and 'C' in the third.
% strcmpi is case insensitive
p = p(strcmpi(p,"ABC"),:)

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Kyle Tan 2021-7-6

编辑：Kyle Tan 2021-7-6

How can I incorporate this formula into a find txt formula?

After finding all information, I need a command to find all possible combinations of a ten letter of strings of D and E only. EX: DDDDDDDDDE, EEEEDEDEDE, etc., in any order and any amount of Ds and Es. While I used the permutation formula, I found that there were 252 results, but only involving the combination of exactly 5 D's and 5 E's. If possible, is there a way to list all possible combinations AND Permutations?

Cris LaPierre 2021-7-7

编辑：Cris LaPierre 2021-7-7

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Not sure of your data format, but I think I would take a slightly different approach here. I would use the pattern searching capabilities of MATLAB to identify the sequences you want.

% using cell arrays
C = {'DDDDDDDDDE','EEEEDEDEDE','EEEEDEDEDA'};
pat = characterListPattern("DE");
inds = count(C,pat,'IgnoreCase',true)==10;
C{inds}
ans = 'DDDDDDDDDE'
ans = 'EEEEDEDEDE'
% using string arrays
txt = ["DDDDDDDDDE","EEEEDEDEDE","EEEEDEDEDA"];
pat = characterListPattern("DE");
inds = count(txt,pat,'IgnoreCase',true)==10;
txt(inds)
ans = 1×2 string array
    "DDDDDDDDDE"    "EEEEDEDEDE"