how to prealloacte and store values in a character array?

Hi! :)

I want to make a character array consisting of 3 rows and 2 strings and firstly I dont know how I can preallocate it. I also tried to store values in it ( in the first row) using the attached code but failed to do so

best_salt_1 = "ZnBr2";
best_salt_2 = "Format";

combinations_of_best_salts=char(zeros(antall_soner,2))
combinations_of_best_salts(1,1:strlength(best_salt_1))=best_salt_1;
combinations_of_best_salts(1,strlength(best_salt_1):18- strlength(best_salt_2))=best_salt_2;
disp(combinations_of_best_salts)

[Stephen23]

Please give us best_salt_1 and best_salt_2, so that we can run your code.

[Muazma Ali]

Best_salt_1= "ZnBr2" Best_salt_2="Format" for instance

[Stephen23]

@Muazma Ali: please show the expected output (not a description).

[Muazma Ali]

@Stephen23 Row one of combinations_best_salts should be : ZnBr2 Format

Answer 1

[Stephen23]

I am guessing that your strings have different lengths on different loop iterations, in which case it mght not be obvious how to preallocate the array.

Here are two alternative approaches:

N = 7; % number of rows

Character array (preallocated rows, expand columns as required):

M = char(nan(N,0));
for k = 1:N
    [S1,S2] = rndstr(k); % random strings
    V = sprintf('%s %s',S1,S2);
    M(k,1:numel(V)) = V;
end
display(M)

M = 7×12 char array
    'd!=.) AFS   '
    '#TIH@ [=:[  '
    'c<Qtu 4%J   '
    'T|db5|! Ij3r'
    'r4wN hQ<2(f '
    '@n$+XRH [JfQ'
    'jJe SP':O`l '

Cell array to collect data, CHAR() after the loop:

C = cell(1,N);
for k = 1:N
    [S1,S2] = rndstr(k); % random strings
    C{k} = sprintf('%s %s',S1,S2);
end
M = char(C{:})

M = 7×12 char array
    'd!=.) AFS   '
    '#TIH@ [=:[  '
    'c<Qtu 4%J   '
    'T|db5|! Ij3r'
    'r4wN hQ<2(f '
    '@n$+XRH [JfQ'
    'jJe SP':O`l '

function [st1,st2] = rndstr(k)
rng(k);
st1 = string(char(randi([33,126],1,randi([3,7]))));
st2 = string(char(randi([33,126],1,randi([3,7]))));
end

[Muazma Ali]

@Stephen23 what is the input k in your last alternative..?

[Muazma Ali]

@Stephen23 can you try to explain what your last alternative does, line by line.., please?

[Stephen23]

"what is the input k in your last alternative..?"

k is the loop iterator. You can find the MATLAB documentation for FOR loops here: https://www.mathworks.com/help/matlab/ref/for.html

It is not clear what you mean by "input k": I provided the iterator as an input to my fake-data generator function in order to reset the random number generator, so that both loops would provide exactly the same random numbers and give exactly the same output character matrix. This is completely superfluous and unrelated to the answer, because of course you would use your strings, not my fake data.

"can you try to explain what your last alternative does, line by line.., please?"

C = cell(1,N);                     % preallocate a cell array to hold character vectors
for k = 1:N                        % loop N times
    [S1,S2] = rndstr(k);           % create fake data strings (you use your strings)
    C{k} = sprintf('%s %s',S1,S2); % create character vector and store in cell array
end                                %
M = char(C{:})                     % join all character vectors into one character matrix

Note that CHAR() automatically pads the character vectors with spaces, in order to create the matrix.

[Muazma Ali]

@Stephen23 thanks, now I understand the code !:)