Find char consecutive in a string

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pamela sulis 2015-11-10

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评论： pamela sulis 2015-11-11

Hi! I have this string

stringa={stringa1; stringa2; stringa3; stringa4};
stringa1='{a(abc)(ac)d(cf)}';
stringa2='{(ad)c(bc)(ae)}';
stringa3='{(ef)(ab)(df)cb}';
stringa4='{eg(af)cbc}';

and I want to find per every string (stringa1, stringa2 ..) the number of 'ab' 'ba'. a and b not must be consecutive. I try strfind but it's not give me the right answer. Can you help me? Thanks

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Guillaume 2015-11-10

I assume you mean a and b must not be consecutive?

Can you show what the answer should be for each of your example string? Can a 'a' be part of several 'ab' string or is it restricted to the closest 'b'.

If you ignore all the other characters is 'a***a***b***b' 1, 2 or 4 occurences?

pamela sulis 2015-11-10

编辑：pamela sulis 2015-11-10

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yes, a e b must not b consecutive.

    For example 'ab'
    stringa1='{a(abc)(ac)d(cf)}'; --> I find 1 'ab'
    stringa2='{(ad)c(bc)(ae)}'; --> I find 1 'ab'
    stringa3='{(ef)(ab)(df)cb}';  --> I find 1 'ab'
    stringa4='{eg(af)cbc}'; ---> I find 1 'ab'
    For example 'ba'
    stringa1='{a(abc)(ac)d(cf)}'; --> I find 1 'ba'
    stringa2='{(ad)c(bc)(ae)}'; --> I find 1 'ba'
    stringa3='{(ef)(ab)(df)cb}';  --> I find 0 'ba'
    stringa4='{eg(af)cbc}'; ---> I find 0 'ba'

I want that the code makes the same... i try strfind but don't give me the answer that i want.

About your question: 'If you ignore all the other characters is 'a***a***b***b' 1, 2 or 4 occurences?' it is one occurences: i want know only if there are 'ab' or 'ba' not the number of time they are in the string.

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Answer 1

Guillaume 2015-11-10

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https://ww2.mathworks.cn/matlabcentral/answers/254062-find-char-consecutive-in-a-string#answer_199190

编辑：Guillaume 2015-11-10

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Thanks for clarifying. You still haven't my answered my question about whether or not a character can be part of several matches or if the matches can intersect (see my 'a***a***b***b' example).

Assuming the answer is no to both questions, the simplest way is to use a regular expression:

stringa1='{a(abc)(ac)d(cf)}';
stringa2='{(ad)c(bc)(ae)}';
stringa3='{(ef)(ab)(df)cb}';
stringa4='{eg(af)cbc}';
stringa={stringa1; stringa2; stringa3; stringa4};
matchstarts = regexp(stringa, 'a.+?b'); %for 'ab'
matchcounts = cellfun(@numel, matchstarts)

The regular expression above says match 'a', followed by as little as necessary (the ?) but at least one (the +) characters, followed by a 'b'.

For 'ba', the regular expression would then be 'b.+?a'

Note that if the answer is yes to either question, regular expressions won't work.

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Guillaume 2015-11-10

'(\a.+?b)\' is a meaningless regular expression.

I'm not clear on what you're trying to match anymore. Can you describe it clearly, in words, the same way I've explained my regular expression.

As I've said '\(a.+?b\)' will match an opening bracket, followed immediately by an 'a' followed by at least one character and as few as possible, followed by a 'b', immediately followed by a closing bracket. It will not match anything else.

pamela sulis 2015-11-11