How to access substrings out of cell array with indexing?

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Osvald Ljungstrand
Osvald Ljungstrand 2016 年 12 月 20 日
コメント済み: Osvald Ljungstrand 2016 年 12 月 21 日
Hi all, I searched a lot through the community as there was normally someone with a similar problem. But this time I was not able to find a solution.
I have a cell array (over 13,000x1) with strings and need to extract the number within. Example:
message = { 'error(1): occured due to A' ; ...
'error(25): occured due to B' ; ...
'error(306): occured due to C' };
With 'regexp' I can identify the position of the number:
[a,e] = regexp(message,'\(\d*\)');
Normally I prefer logical indexing but couldn't find a nice solution to access the substrings within a cell array. So for this small array I can extract the number with a loop
number = zeros(size(message,1),1);
for i=1:size(message,1)
number(i) = str2double(message{i}(a{i}+1:e{i}-1));
end
But the for-loop is very time consuming for big cell arrays. I would prefer to use the existing a and e array.
Does anyone has a better way to access substrings within cell arrays?

採用された回答

Andrei Bobrov
Andrei Bobrov 2016 年 12 月 20 日
message = { 'error(1): occured due to A' ; ...
'error(25): occured due to B' ; ...
'error(306): occured due to C' }
a = regexp(message,'\d+','match','once')
out = str2double(a)

その他の回答 (1 件)

David Barry
David Barry 2016 年 12 月 20 日
If you are using R2016b then you can make use of the new String datatype and then use the extractBetween function. This should be very quick.
message = { 'error(1): occured due to A' ; ...
'error(25): occured due to B' ; ...
'error(306): occured due to C' };
message = string(message);
nums = extractBetween(message, '(', ')');
nums = str2double(nums);
  2 件のコメント
David Barry
David Barry 2016 年 12 月 20 日
Or see Andrei's answer if you are using an older release.
Osvald Ljungstrand
Osvald Ljungstrand 2016 年 12 月 21 日
Nonehteless my "message" looks a bit more complex and I can't just copy paste your suggestion, the combination of the 'match' option for regexp with the extractBetween function will solve my problem perfectly. Thank you a lot for your help

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