# Extracting second number after comma within parenthesis

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SATINATH DEBNATH on 20 Jan 2020
Edited: Stephen23 on 21 Jan 2020
I have a string
"Toc(Clock Data Ref Time) : 0x91E6 (37350,5.976000e+005 s)";
I am looking to extract only contents after comma from the second parenthesis.
So, the required would be 5.976000e+005.
My code is
XX="Toc(Clock Data Ref Time) : 0x91E6 (37350,5.976000e+005 s)";
TOC=strrep(XX,'Toc(Clock Data Ref Time)','');
TOC=regexp(TOC, '(?<=\()[^)]*(?=\))', 'match')
Which returns 37350,5.976000e+005 s.
But how to extract numbers after comma?
Thank you.

Allen on 20 Jan 2020
Assuming that the number will always be in scientific notation, then the following should work.
TOC = regexp(str,'(?<=\(.*?,)\d\.\d+e\+\d+(?=.*?\))','match');
% A rough description of what pattern the expression is indicating
% (?<=\(.*?,) Look behind an open parenthesis for an optional set of any characters until reaching the following pattern
% \d\.\d+e\+\d+ A single digit followed by a period, followed by 1 or more consecutive digits, followed by e+,
% followed by 1 or more consecutive digits.
% This pattern this must precede the following look-ahead assertion.
% (?=.*?\)) Any optional set of characters before a closed parenthesis.
Stephen23 on 21 Jan 2020
Edited: Stephen23 on 21 Jan 2020
The regexp documentation is more focussed on the function itself, for detailed documentation on regular expressions in MATLAB read this (and the links at the bottom of that page):

dpb on 20 Jan 2020
Slightly modified version following IA's direction using newer string parsing functions that can do much of what regexp expressions are often used for--
XX = "Toc(Clock Data Ref Time) : 0x91E6 (37350,5.976000e+005 s)";
TOC=str2double(extractBetween(XX,',',' '));
>> TOC
TOC =
597600
>>
##### 2 CommentsShowHide 1 older comment
dpb on 20 Jan 2020
Edited: dpb on 20 Jan 2020
I discovered them when exploring the new strings class back when it was introduced.
They're not that easy to find on their own, however, the "See Also" links don't include them in many logical places like under any of the historical strfind strcmp routines nor even with string itself. They're listed under a topic "Search and Replace Text" but it's a long and arduous road to even get to that link from top level.
I've made the suggestion documentation needs more links to help make them visible but so far hasn't made it to the top of the list (which I reckon must be miles long)...

Image Analyst on 20 Jan 2020
If your format is fixed (the same every time), you can do it much, much more simply, and less cryptically, by avoiding regexp() and simply using indexing:
XX = "Toc(Clock Data Ref Time) : 0x91E6 (37350,5.976000e+005 s)";
% Convert from string to character array.
XX = char(XX);
% Extract known, fixed part of string from between 47 and 59, inclusive.
TOC = XX(47:59) % This is a character array. Use str2double() if you want a number.
Image Analyst on 21 Jan 2020
You gave XX as a string class variable, not as a character array, so that's why I had to use XX=char(XX). If your data is already a character array just delete that line because (for some reason) indexing doesn't seem to work with strings. Otherwise, attach XX in a .mat file if you're still interested in pursuing the strfind() method.

Stephen23 on 20 Jan 2020
Simply match all text from the comma to the whitespace:
>> str = 'Toc(Clock Data Ref Time) : 0x91E6 (37350,5.976000e+005 s)';
>> regexp(str,'(?<=,)\S+','match')
ans =
'5.976000e+005'
dpb on 21 Jan 2020
Edited: dpb on 21 Jan 2020
Then the substring selection between str(i1:i2) will. Of course, one can roll your own version of extractBetween that way as well...altho regexp() then may well be a better choice.

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