Working with the MIT arrhythmia database annotations: how can I convert the characters into numbers?

Question

Ioana Cretu 2021-2-22

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回答： Shadaab Siddiqie 2021-2-25

I work with MIT arrhythmia database and I want to group the annotations given for each beat in 5 classes, such as:

N={'N','L','R','e','j'}; %non_ectopic_beat
S={'A','a','J','S'};     %supra_ventricular_ectopic_beat
V={'V','E'};             %ventricular_ectopic_beats
F={'F'};                 %Fusion_beat
non_beats={'+','/','f','Q'};

How can I search into the annotation files of each ECG signal and replace the letter from those 5 groups with numbers from 1 to 5?

For example, when I have any of the non-ectopic beats ('N', 'L','R','e', or 'j' ) I want to have the label 1. For the secong class ('A','a','J','S') I want to have label 2 and so on.

I am also opened to other suggestion, as my goal is to append these annotatios to the feature set that I extracted from these signals.

The annotations files are in 'atr' format and I read them using the WFDB toolbox:

[ann,anntype]=rdann('100','atr'); 
%ann has the location of the R peak and anntype has the annotation of each heartbeat
anntype =
  2274×1 char array
    '+'
    'N'
    'N'
    'N'
    'N'
    'N'
    'N'
    'N'
    'A'
    'N'
    'N'
    'N'
 ...

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dpb 2021-2-22

You can certainly make a small piece and attach it..."help us help you!"

Ioana Cretu 2021-2-22

ann.txt

I attached a txt file with the annotations from one patient, hope it helps

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Answer 1

Shadaab Siddiqie 2021-2-25

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https://ww2.mathworks.cn/matlabcentral/answers/752744-working-with-the-mit-arrhythmia-database-annotations-how-can-i-convert-the-characters-into-numbers#answer_632809

在 MATLAB Online 中打开

From my understanding you want to replace few strings to few particular numbers. Here is the code which might help you.

content = fileread( 'ann.txt' ) ;
content = strrep( content, 'N', '1' ) ;
content = strrep( content, 'L', '1' ) ;
content = strrep( content, 'V', '3' ) ;
content = strrep( content, '+', '5' ) ;
fId = fopen( 'MyData_updated.txt', 'w' ) ;
fwrite( fId, content ) ;
fclose( fId ) ;