Read data from string
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I have string line:
x='abc123(xyz456)'
How to read information only in brackets, to have result:
y='xyz456'.
采纳的回答
>> x='abc123(xyz456)';
>> regexp(x,'(?<=\().+(?=\))','match')
ans =
'xyz456'
This command uses regexp and, specifically, lookaround assertions. It's basically saying, if you find a group of characters, look behind to see if there is an "open parenthesis" character and look ahead to see if there is a "close parenthesis" character. If so, return all the characters between them.
6 个评论
Azzi Abdelmalek
2013-8-7
This will not work if
x='abc123(xyz456)ab(cde)';
True. It assumes only one set of parenthesis. I used the character identifier in case of spaces, but that might not be a needed flexibility. Regardless, I suppose a better version to account for that would be similar to yours:
regexp(x,'(?<=\()[\w\s]+(?=\))','match')
per isakson
2013-8-7
or
x='abc123(xyz456)aaa(123)mmmm';
regexp(x,'(?<=\().+?(?=\))','match')
where the added ? stands for
Lazy expression: match as few characters as necessary.
My preference goes to Per lazy expr., but I wanted to mention the following, counter-intuitive behavior:
>> tok = regexp('_A_A-', '_(.*?)-', 'tokens')
tok =
{1x1 cell}
>> tok{1}
ans =
'A_A'
and not just A, as many people would expect.
per isakson
2013-8-7
编辑：per isakson
2013-8-7
Surprise!
regexp('_A_A-', '(?<=_)[^_]+?(?=-)', 'match' )
ans =
'A'
Thus, doc should say something like
Lazy expression: match as few characters as necessary **downstream**.
Yep, in other words, it stops when it matches the last part of the pattern for the first time (lazy), but it doesn't pull back the starting point (the tail? ;-)) to minimize the match (not that lazy finally, or really really lazy in fact). Thankfully, you see/understand this once and you never forget it!
更多回答（2 个）
Azzi Abdelmalek
2013-8-7
y=regexp(x,'(?<=\()[\w]+(?=\))','match')
1 个评论
Azzi Abdelmalek
2013-8-7
%or
x=x='abc123 (xyz 45_6) ddd (rtr)ccc'
y=regexp(x,'\(([\w\s]+)\)','tokens');
celldisp(y)
Jan
2013-8-7
x = 'abc123(xyz456)';
ini = strfind(x, '(');
fin = strfind(x, ')');
key = x(ini(1) + 1:fin(1) - 1);
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