How to get a desired result using regexp in matlab

I am evaluating a matlab expression: I have an expression like this:

exp2 = '[^(]+.*[^)]+'; I have a variable str ='(1,2,3)' I want to evaluate a regexp as follows:

regexp(str,exp2,'match');

and this works and i get a result:'1,2,3'

the same goes for when str ='(1m)' result is '1m'

But when str ='(1)' the result is { }

What should i do to get a result ='1'

Kindly help me with this.Thank you in advance

Answer 1

[Rik]

Just like Stephen, I would also suggest changing your expression.

exp2 = '[^()]';
str1 ='(1,2,3)';
str2='(1)';
[start_idx,end_idx]=regexp(str1,exp2);
str1(start_idx)
[start_idx,end_idx]=regexp(str2,exp2);
str2(start_idx)

Answer 2

[Stephen23]

Why do you need regular expressions for this? Why not just str(2:end-1) ?:

>> str = '(1,2,3)';
>> str(2:end-1)
ans = 1,2,3
>> str = '(1m)';
>> str(2:end-1)
ans = 1m
>> str = '(1)';
>> str(2:end-1)
ans = 1

Or perhaps use regexprep, which would make your regular expression simpler (because it is easier to match what you don't want):

>> str = '(1,2,3)';
>> regexprep(str,'^\(|\)$','')
ans = 1,2,3
>> str = '(1m)';
>> regexprep(str,'^\(|\)$','')
ans = 1m
>> str = '(1)';
>> regexprep(str,'^\(|\)$','')
ans = 1

[Giri]

Hi Stephan,

Can you explain the expression please?

[Stephen23]

^\(     % matches parenthesis at start of string
   |    % or
    \)$ % matches parenthesis at end of string

Any match is replaced by '', i.e. is removed from the input.

[Giri]

aah ok thanks.. i did not realise that you were replacing the string. Thanks a lot Stephen.