how to extract date from a txt file while skipping other data?

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Imtiaz nabi 2022-1-13

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https://ww2.mathworks.cn/matlabcentral/answers/1628280-how-to-extract-date-from-a-txt-file-while-skipping-other-data

编辑： per isakson 2022-1-14

Hi there, I am reading GPS/GNSS ephemeris file and have extracted the data from the .nav file but I am confused about extracting the data from the file. Can anyone please help me? I want to extract the date from the .nav file and convert it into GPS time.

to better understand my uestion please read the attached image. The highlighted columns in row 8, row, 16 and so on represents time in Year, Month, day, hour, minute and second format. for example in row 18 after the satellite 22 this is basically 2019/7/31 2:00:00.

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Cris LaPierre 2022-1-13

It's hard to help from a screenshot. Please attach a sample file for us to use using the paperclip icon.

per isakson 2022-1-14

编辑：per isakson 2022-1-14

在 MATLAB Online 中打开

Extracting the date substrings can be done with chr = fileread(...) and regexp(...) (, I guess.)

%%
chr = { '22 19  7 31  2  0  0.0 -7.379'
    '0.0 1.1 2.2 3.3 4.4 5.5 6.6 9'
    '30 19  8  1  2  0  0.0 -7.379' };
chr = strjoin( chr, '\n' );
xpr = '(?<=\d{2})\x20+\d{1,2}\x20+\d{1,2}\x20+\d{1,2}\x20+\d{1,2}\x20+\d{1,2}[0-9\.]+';
cac = regexp( chr, xpr, 'match' )
cac = 1×2 cell array
    {'  7 31  2  0  0.0'}    {'  8  1  2  0  0.0'}