date time from filename

Hi there I need to read the date and time from a series of filenames (4) that are not fully sync. First I'm struggling to only get the date and time (e.g., P02_PRO_ST_20221115_151337.csv). In the example, the part with '20221115_151337'. Secondly, I'm also struggling to convert the second half (i.e.,'151337') to time, which is the variable part across my 4 files. I need the latter as it is the start of the timestamp (in milliseconds) of my timeseries within the files and which I will use to sync the signals in the files. I tried the following:

p = 2;

folx = {'/Volumes/SSD_T7/March/'};

basename = strcat(folx,'P0',num2str(p),'/','P0',num2str(p),'_PRO_'); % all files have same 'prefix'

listoffiles = dir(strcat(basename,'*','.csv')); % JUST NOT WORKING

Since the above is not working the I cannot move to use the following to extract the date and time for each of my files;

[~,name,~] = fileparts(filename);

Many thanks for your help

Eduardo

[Stephen23]

First lets create some fake data files just for testing the code:

writematrix(1:3,'P02_PRO_ST_20221115_151337.csv')
writematrix(4:6,'P02_PRO_ST_20221115_151338.csv')
writematrix(7:9,'P02_PRO_ST_20221115_151339.csv')

Now lets get a list of the filenames:

P = 2;
D = '.'; % absolute/relative path to where the file are saved
B = sprintf('P0%d_PRO_ST_*.csv',P);
S = dir(fullfile(D,B));
[~,fnm,~] = fileparts({S.name})

fnm = 1×3 cell array
    {'P02_PRO_ST_20221115_151337'}    {'P02_PRO_ST_20221115_151338'}    {'P02_PRO_ST_20221115_151339'}

It is easy to convert the datestamp to DATETIME objects and then the time of day as DURATION objects:

tmp = regexp(fnm,'\d+_\d+$','match','once');
dtm = datetime(tmp,'InputFormat','uuuuMMdd_HHmmss') % convert to DATETIME

dtm = 1×3 datetime array
   15-Nov-2022 15:13:37   15-Nov-2022 15:13:38   15-Nov-2022 15:13:39

tod = timeofday(dtm) % get the time of day

tod = 1×3 duration array
   15:13:37   15:13:38   15:13:39

As Mathieu NOE already commented, you should replace string concatenation with FULLFILE (and also NUM2STR with SPRINTF or COMPOSE).

Answer 1

[Mathieu NOE]

hello

try this code below

I use fullfile instead of your method to concat folder and basename

your path and filenames should now appear in structure S (that you can further expand to integrate other results from your computations)

fileparst is not really needed for what you want to do

% folx = 'C:\Users\A0H36019\Documents\P02' ; % my folder for my tests
folx = '/Volumes/SSD_T7/March/P02' ; % your folder for your  tests

p = 2;
basename = ['P0',num2str(p),'_PRO_*.csv']; % all files have same 'prefix'

S = dir(fullfile(folx,basename)); % get list of data files in directory

%% optionnal 
% S = natsortfiles(S); % sort file names into natural order (better than regular dir command) , see FEX submission : 
% %            %(https://fr.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort)


for k = 1:length(S)
    
    filename = S(k).name % display filenames in command window : check they are sorted as needed (use natsortfiles if dir is not doing it right)
    
    % extract the numerical arrays date and time from filename char array
    ind_underscore = strfind(filename,'_');
    % date
    date_str = filename(ind_underscore(end-1)+1:ind_underscore(end)-1);
    year = str2num(date_str(1:4)) % year
    month = str2num(date_str(5:6)) % month
    day = str2num(date_str(7:8))  % day
    % time
    ind_dot = strfind(filename,'.');
    time_str = filename(ind_underscore(end)+1:ind_dot-1);
    hours = str2num(time_str(1:2)) % hours
    minutes = str2num(time_str(3:4)) % minutes
    seconds = str2num(time_str(5:6))  % seconds    
    
    
    % insert your own code below

	

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