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Regular expressions: dealing with spaces

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pietro on 3 May 2016
Commented: Jan on 25 Oct 2017
Hi all,
I have different strings wich they differ from the number of spaces among words. I need to find a way to find this string pattern in a long string.
For example
TxT='f 2000 min';
TxT='f 2000 min';
At first, I came up with this,
regexp(Txt,'(f \d+ min)||(of\d+min)','match')
but it doesn't work for the last case for the number of spaces. Is there any way to not consider spaces into regular expressions or that a variable number of spaces inside the string might be in the strings?


Guillaume on 3 May 2016
Note that OR in regular expressions is a single bar |, your regular expression would theoretically match an empty string (it doesn't because the regular expression engine never matches empty)
See Stephen's answer for the solution. Do not use | when you only need to change the number of times a character needs to be match. It will usually be slower than just using quantifiers (*, ?, +, {m, n}, {m,}, or {n})

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Accepted Answer

Stephen Cobeldick
Stephen Cobeldick on 3 May 2016
Edited: Stephen Cobeldick on 3 May 2016
You were almost there:
>> fmt = 'f *\d+ *min';
>> regexp('f 2000 min',fmt,'match')
ans =
f 2000 min
>> regexp('f2000min',fmt,'match')
ans =
>> regexp('f 2000 min',fmt,'match')
ans =
f 2000 min
One of the best things about MATLAB is the great documentation. It means that you don't have to guess how MATLAB works, or ask random strangers on internet forums. The documentation is online, and searchable using your favorite internet search engine. And when I searched for ˇMATLAB regular expression", this is the first result:
It explains how to specify how many times characters or patterns should be matched. Isn't that great: we can read the help and learn how to use MATLAB! If you had done this you would have learned how to use the vertical bar correctly.


Jan on 25 Oct 2017
I have remove the flag. Stephen's answer contains a solution and is polite. It is not ironic to suggest to use the documentation, but useful.

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