regexp: Extract optional named tokens
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I would like to extract some information from the following text:
![text.PNG](https://www.mathworks.com/matlabcentral/answers/uploaded_files/227203/text.png)
There are 3 groups in the text. I want to extract the genders (enclosed in brackets), the group names (the text following 'Name:') and the student IDs for each group (the numbers following 'ID XX =').
My desired output is as follows:
![struct.PNG](https://www.mathworks.com/matlabcentral/answers/uploaded_files/227204/struct.png)
The issue is that not all groups have a header line (the lines starting with '#'), e.g. for group 3.
My code is as follows
str = fileread('trip-data.txt');
expr = 'Student group.+?\((?<Gender>\w+?)\).*?Name:(?<Name>.+?)\nGROUP.+?=(?<IDs>.+?(,\s*\n.+?)*)(?=(\n|$))';
groups = regexp(str, expr, 'names');
The returned struct array ignores group 3:
![Capture.PNG](https://www.mathworks.com/matlabcentral/answers/uploaded_files/227205/Capture.png)
I have also tried enclosing the header line in an optional bracket, e.g. '()?', like so
expr = '(Student group.+?\((?<Gender>\w+?)\).*?Name:(?<Name>.+?))?\nGROUP.+?=(?<IDs>.+?(,\s*\n.+?)*)(?=(\n|$))';
The returned struct captures the 'ID' fields but not the 'Gender' and 'Name' fields for all 3 groups:
![Capture1.PNG](https://www.mathworks.com/matlabcentral/answers/uploaded_files/227206/Capture1.png)
2 Comments
Rik
on 2 Jul 2019
Do you absolutely need to use a regexp? Because it might be easier with other tools (if maybe slightly less efficient).
Answers (1)
Akira Agata
on 3 Jul 2019
Edited: Akira Agata
on 3 Jul 2019
How about extracting 'Name', 'Gender' and 'ID' one-by-one?
The following is an example.
% Read the file
str = fileread('trip-data.txt');
% Remove newline in ID
str = regexprep(str,'\r\n\s+','');
% Remove newline after 'Name: XX'
str = regexprep(str,'(Name:\s+\w+)\r\n','$1, ');
% Store each line as a cell array
c = strsplit(str,'\r\n')';
% Extract one-by-one
Name = erase(regexp(c,'Name:\s(\w+)','match','once'),'Name: ');
Gender = regexp(c,'(male|female)','match','once');
ID = strtrim(extractAfter(c,'='));
% Summarize as a table
tbl = table(Name,Gender,ID);
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