How can I find each character's index within a matrix, from a vector of characters?

I have a matrix of characters

Letters = [A, B, C;

D, E, F;

G, H, I];

Secondarily, I will have a vector of letters, and I need to find the index of each letter in the matrix of Letters. For example,

vec = [A, C, H, I], or it could be any combination of letters. I'm sure there is a simple answer that I am missing. I know normally you need to call the character with a string, but I don't know how to call, say vec(1) as a string (as in, idx = find(Letters == vec(1)), and it would return 1, for A), which I think would solve the problem.

Answer 1

[Chunru]

Letters =['ABC'; 'DEF'; 'GHI']

Letters = 3×3 char array
    'ABC'
    'DEF'
    'GHI'

vec = 'ACHI'

vec = 'ACHI'

for i=1:length(vec)
    [r, c] = find(Letters == vec(i));
    fprintf("%s:  (%d, %d)\n", vec(i), r, c)
end

A:  (1, 1)
C:  (1, 3)
H:  (3, 2)
I:  (3, 3)

Answer 2

[DGM]

If you're talking strictly about character arrays, then:

Letters = ['ABC'; 'DEF'; 'HIJ'];
vec = 'ACHI'; 

[~, idx] = ismember(vec,Letters) % idx is a linear index into Letters

idx = 1×4

1 7 3 6