I want to initialize a very large character array with the same character string

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David
David 2013-6-4
The array is so large it takes forever for MATLAB to do it with a simple loop, e.g.;
for i = 1:N A(i) = 'String' end
I know this can be done numerically using ones (* the desired value) in a single line of code. Can it be done with a character string in a way that speeds up the process?
Thanks, David
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Jan
Jan 2013-6-4
编辑：Jan 2013-6-4
The shown loop cannot work, because you try to assign a CHAR vector to a scalar element. What is the wanted result? Do you want a cell string {'String', 'String', ...} or a CHAR vetor 'StringString...'?

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回答（2 个）

Iain
Iain 2013-6-4
char_array = char(ones(N,1) * 'String');
cell_version = repmat({'String'},N,1);
Ahmed
Ahmed 2013-6-4
Have you tried 'repmat'?
N = 100000;
A = repmat('String',N,1);
If you must use a for-loop, you should pre-allocate the array. If uninitialized, the growing of the array will consume a lot of time. Here, an example of preallocation and filling with loop.
N = 100000;
A = repmat(char(0),N,6);
for i = 1:N, A(i,:) = 'String'; end
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Jan
Jan 2013-6-4
It is much faster to operate on the columns and assign scalars:
N = 100000;
A = repmat(char(0),N,6);
S = 'String';
for k = 1:6
A(:, k) = S(k);
end

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