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How to assign a column of text string to another variable?

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Leon
Leon on 9 Mar 2020
Commented: Guillaume on 9 Mar 2020
For example,
A = repmat('test', 5,1);
If I want to assign A to B, why the below doesn't work? What is the right way to do it?
B([20+1:20+5,1) = A
Many thanks,

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Adam Danz
Adam Danz on 9 Mar 2020
Yes, it's problematic. Your definition of B creates a double precision numeric vector. But A is a char array.
Perhaps you're looking for
% Cell array of chars
A = repmat({'test'}, 5,1);
B = cell(100000,1);
B([20+1:20+5]) = A;
or
% String array
A = repmat("test", 5,1);
B = repmat("", 100000,1)
B([20+1:20+5]) = A;
Leon
Leon on 9 Mar 2020
Thank you! How do I define a N by 1 column of strings or chars?
Leon
Leon on 9 Mar 2020
Thank you so much. It works
The string array is what I need!

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Accepted Answer

Guillaume
Guillaume on 9 Mar 2020
A = repmat('test', 5,1);
replicates the 1x4 char array 'test' 5 times along the rows, resulting in a 5x4 matrix of 20 characters
B([20+1:20+5,1) = A
attemps to store these 20 characters at indices 21 to 25 of row 1 of B. That's room for just 5 characters, so yes it's not going to work.
Note that you're working with char vectors, not string arrays. Perhaps you intended to work with string arrays. char vectors and string arrays work differently. Your code would work with string arrays. string arrays use ", not ' as the enclosing symbol:
%this would work. No idea if that's what you want
A = repmat("test", 5, 1);
B(20+(1:5), 1) = A;
However, note that you don't even need the repmat in the above. Assigning a scalar to a vector automatically replicates the scalar:
A = "test";
B(20+(1:5), 1) = A;

  2 Comments

Leon
Leon on 9 Mar 2020
Thanks!
Unfortunately, when I test it, my 21 to 25 rows are NaNs.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
NaN
NaN
NaN
NaN
NaN
Guillaume
Guillaume on 9 Mar 2020
If you're using strings, then B needs to be a string array to starts with. If it's starts as a numerical array then yes the strings will be converted to numbers and "test" not being a valid representation of a number gets converted to NaN (Not a Number).
B = strings(0);
%or
B = string.empty
would create an empty string array. Alternatively,
clear B
A = "test";
B(20+(1:5), 1) = A;
also works.

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