how to prealloacte and store values in a character array?

Question

Muazma Ali 2022-8-2

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编辑： Stephen23 2022-8-12

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)

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Stephen23 2022-8-2

编辑：Stephen23 2022-8-2

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

Muazma Ali 2022-8-2

编辑：Muazma Ali 2022-8-12

@Stephen23 Row one of combinations_best_salts should be : ZnBr2 Format

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Answer 1

Stephen23 2022-8-12

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https://ww2.mathworks.cn/matlabcentral/answers/1772615-how-to-prealloacte-and-store-values-in-a-character-array#answer_1025400

编辑：Stephen23 2022-8-12

在 MATLAB Online 中打开

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

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Stephen23 2022-8-12

编辑：Stephen23 2022-8-12

在 MATLAB Online 中打开

"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