Regular expressions: dealing with spaces

Question

pietro 2016-5-3

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https://ww2.mathworks.cn/matlabcentral/answers/282330-regular-expressions-dealing-with-spaces

编辑： Stephen23 2021-4-21

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='f2000min';
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?

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Guillaume 2016-5-3

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})

pietro 2016-5-3

Thank you so much.

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Answer 1

Stephen23 2016-5-3

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/282330-regular-expressions-dealing-with-spaces#answer_220574

编辑：Stephen23 2021-4-21

在 MATLAB Online 中打开

You were almost there:

>> fmt = 'f *\d+ *min';
>> regexp('f 2000 min',fmt,'match')
ans =
f 2000 min
>> regexp('f2000min',fmt,'match')
ans =
f2000min
>> 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:

http://www.mathworks.com/help/matlab/matlab_prog/regular-expressions.html

It explains how to specify how many times characters or patterns should be matched.