date time from filename

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Luis Eduardo Cofré Lizama
移动：Stephen23 2023-7-29
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
  1 个评论
Stephen23
Stephen23 2022-11-16
移动：Stephen23 2023-7-29
Ran in:
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).

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采纳的回答

Mathieu NOE
Mathieu NOE 2022-11-16
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
end

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