Check if UTF-8 letter is vowel in MATLAB

Question

I found a simple way to check whether a letter is a vowel in MATLAB (from here), simply like this :

is_vowel = numel(regexp(letter,'[aeiouAEIOU]'))>0

However, in my language (Turkish), the list of vowels is actually this:

is_vowel = numel(regexp(letter,'[aeiouöüıAEIOUÖÜİ]'))>0

this works correctly for ö and ü (Also for capitals) but it returns 0 for ı and İ. How can I solve this issue so it returns 1 for all the letters in the second list?

P.S. : I will use this code as a base for the latter part of my project which will involve things like getting the number of vowels in a word, so I'm open to alternative solutions too.

Also, if no other way is found, I'm ok with converting the letters to their English counterparts (like Ö to O etc.) but I prefer not changing them.

Thanks for any help!

Edit

I now see that the related part of my .m file is converted to this :

regexp(letter,'[aeiouöü?AEIOUÖÜ?]');

This is probably why regex is not working on those two characters. Any way to save these characters correctly in an *.m file?

Solution

Thanks to @AndrasDeak :

function [b] = is_vowel(letter)
b = ismember(letter,['aeiouöüAEIOUÖÜ' 304 305]);
end

[This](http://stackoverflow.com/a/6872642/5067311) might be helpful, like the function `str = native2unicode(b,'UTF-8');` — Andras Deak -- Слава Україні, Sep 20 '15 at 16:36
Although it would also seem that string literals containing utf8 characters might be problematic... (see comments at linked answer) — Andras Deak -- Слава Україні, Sep 20 '15 at 16:42
You could try and see how a given Turkish letter is represented as a number. I mean like with `letter+0` (I'm not sure about the function that's for this, probably `int`). Then you could try checking that *value* against those few values which are the Turkish vowels. Are you following? — Andras Deak -- Слава Україні, Sep 20 '15 at 17:04
@AndrasDeak thanks for your help! I was AFK; I will now try these. — jeff, Sep 20 '15 at 18:29
Note that `letter+0` is just for printing. Matlab can interpret `letter == 304` as it is. — Andras Deak -- Слава Україні, Sep 20 '15 at 18:38
Checking with the integer value works. If no better / faster answer exists, you can post this as an answer so I can accept it. But please see my first edit. The problem looks related to file encoding. I tried changing it in Notepad++ but it messed it up even worse. — jeff, Sep 20 '15 at 18:40
Tip: instead of regexp, use your string as a char array, which it is, and use `ismember`: `ismember(letter,['aeiouöüAEIOUÖÜ' 304 305])`. That should be faster. Regexp is actually quite slow and bulky anyway. — Andras Deak -- Слава Україні, Sep 20 '15 at 18:41
Wow, thank you so much. This is much more elegant than mine. Please post this as an answer :) — jeff, Sep 20 '15 at 18:46

score 4 · Accepted Answer · answered Sep 20 '15 at 18:52

As we revealed in comments, the problem is that some Turkish characters are incompatible with matlab, but only as string literals. The solution is to check the problematic letters by their value rather than as characters.

A fast solution is based on using ismember to check if the given letter is among the set of Turkish vowels:

b = ismember(letter,['aeiouöüAEIOUÖÜ' 304 305]);

This makes use of the fact that strings are integer vectors under the hood.

And just to overdo it a bit, you can also define this as an anonymous function:

is_vowel = @(letter) ismember(letter,['aeiouöüAEIOUÖÜ' 304 305]);

Check if UTF-8 letter is vowel in MATLAB

Edit

Solution

1 Answers1