MATLAB: Matching substrings with regexp

parseregexpstrings

I'm trying to identify the subexpressions of a formula such as (real cases much longer):

y = ((a + b) * (c / d) + ( e + f ))

The subexpressions are always separated by pairs of parenthesis as in the example above. It seems like I should be able to use a regular expression with a rule like (intuitively) match "an initial left parenthesis, any characters (but no parenthesis), and a terminating right parenthesis" to get:

(a + b) (c / d) (e + f)

Can anybody suggest a regular expression to do this? Or any way other than a regular expression?

Best Answer

subexpressions = regexp(expression, '\([^()]+\)', 'match')

will match any sequence with two brackets enclosing one or more non-bracket.

Related Solutions

MATLAB: Regex: Extract then delete

"Is there a regex function that can extract matched strings and delete them after?"

Not really.

You could do something like this with regexprep and dynamic expressions to store the matched data in a workspace variable, but this will be slow, complex, and rather fragile.

One simple and efficient workaround would be to use both the match and split outputs: this example matches and removes the digits, leaving only the alphabetic characters:

>> S = 'abcd1234efghi6789jklm';
>> [X,Y] = regexp(S,'\d+','match','split');
>> Z = [Y{:}] % the new string with substrings removed
Z =
abcdefghijklm
>> X{:} % the matched substrings
ans =
1234
ans =
6789

MATLAB: How can I extract special contents of a text

regexp(yourstring, '(?<=\()[^)]+', 'match')

should do it. It matches any sequence of anything but closing brackets preceded by an opening bracket. Note that the opening bracket has to be escaped as it's a special character in regexes.

Best Answer

Related Solutions

MATLAB: Regex: Extract then delete

MATLAB: How can I extract special contents of a text

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