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Converting entire cell array to strings

Asked by Rainer on 3 Jun 2015
Latest activity Edited by per isakson
on 5 Jun 2015
x={'words',10,20,30,'more words'}
How do I convert the entire cell array above to strings?

  2 Comments

x{1} and x{5} are already strings. Do you want to scan the cell array and convert the cells that have numbers in them to strings? Or do you want 5 separate string variables, like x1, x2, x3, x4, and x5?
x1 = x{1}
x2 = num2str(x{2});
x3 = num2str(x{3});
x4 = num2str(x{4});
x5 = x{5};
I want to have a generalized solution where I can convert a cell array which is randomly populated with doubles and strings.
{'words',10,20,30,'more words',10,9} becomes {'words','10','20','30','more words','10','9'}
{94,'cows',10,'dogs',30,10,'cats','birds'} becomes {'94','cows','10','dogs','30','10','cats','birds'}

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2 Answers

Answer by Azzi Abdelmalek
on 3 Jun 2015
 Accepted Answer

x={'words',10,20,30,'more words'}
out=cellfun(@num2str,x,'un',0)

  2 Comments

It works because num2str just return the string unchanged when given a string.
edit: As pointed out by per, this relies on the undocumented and actually unexpected behaviour of num2str. Such code could break in the future. (But mathworks also often breaks documented behaviour)
Excellent! Thanks Azzi

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Answer by per isakson
on 3 Jun 2015

is this close to what you want?
>> strsplit( strjoin(x), ',')
ans =
'words' '10' '20' '30' 'more words'

  7 Comments

The solution with num2str relies on the undocumented (AFAIK) feature that a string input is returned as output.
And I don't find a suitable words to comment on
>> num2str('ten')
ans =
ten
>> int2str('ten')
ans =
116 101 110
You're right the behaviour of num2str with string inputs is not documented and kind of unexpected. If num2str adhered to its documentation it should throw an error when passed a string. Sloppy coding or sloppy documenting.
Perhaps matlab should have a ToString function like java and .Net.
The behaviour of int2str makes sense to me. It's equivalent to
num2str(uint16('ten'));
It doesn't help the beginner, me included, that the two functions, num2str and int2str handle string inputs differently.
Yes, "the behavior of int2str makes sense" and that's because it dates back to the beginning of Matlab when everything was numerical arrays. A string was just another way to interpret the array. (My mental model.) By the way, I use strfind to search for sequences of whole numbers in double arrays. I think of that as "us' trick".
However, this behavior of int2str is not documented(?)
There are a number of fundamental function, which converts strings to vectors of ascii-numbers. That is not explicitly stated in the documentation(?)
>> real('ten')
ans =
116 101 110
>> uint16('ten')
ans =
116 101 110
Enough ranting for now!

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