MATLAB Answers

read date from character string

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pruth
pruth on 5 Nov 2015
Commented: pruth on 5 Nov 2015
hi... i have data files(HDF5 format) ... in different sub folders. there are around 50,000 files. i have made a program to pick all HDF5 files from all subfolders and read. there is date and time in thair names which i want read. file names are like bellow
GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151031233116_051_METOPB_16186_DLR_03.HDF5
GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101001652_051_METOPA_46873_DLR_03.HDF5
GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101011234_051_METOPB_16187_DLR_03.HDF5
GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101015816_050_METOPA_46874_DLR_03.HDF5
GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101025358_051_METOPB_16188_DLR_03.HDF5
GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101033940_050_METOPA_46875_DLR_03.HDF5
datenum(filename(42:56),'yyyymmddHHMMSS'); %% to read date and time from file name
this works fine but problem occurs when name of the file changes .there are few files whose names are different than above.for eg.
GOME_O3-NO2-NO2Tropo-BrO-H2O-HCHO_L2_20070920104919_049_METOPA_04770_DLR_03.HDF5
in this file some characters are missing (-SO2)
when i run a loop it runs properly but when loop find this type of name it stops there and said error. i can not delete this files.hope you understand my question.

Accepted Answer

Stephen
Stephen on 5 Nov 2015
Edited: Stephen on 5 Nov 2015
This is easy using regexp to match the date substring:
C = {'GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151031233116_051_METOPB_16186_DLR_03.HDF5'
'GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101001652_051_METOPA_46873_DLR_03.HDF5'
'GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101011234_051_METOPB_16187_DLR_03.HDF5'
'GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101015816_050_METOPA_46874_DLR_03.HDF5'
'GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101025358_051_METOPB_16188_DLR_03.HDF5'
'GOME_O3-NO2-NO2Tropo-BrO-SO2-H2O-HCHO_L2_20151101033940_050_METOPA_46875_DLR_03.HDF5'
'GOME_O3-NO2-NO2Tropo-BrO-H2O-HCHO_L2_20070920104919_049_METOPA_04770_DLR_03.HDF5'};
D = regexp(C,'\d{14}','match','once');
E = datenum(D,'yyyymmddHHMMSS');
and the output:
>> datevec(E)
ans =
2015 10 31 23 31 16
2015 11 1 0 16 52
2015 11 1 1 12 34
2015 11 1 1 58 16
2015 11 1 2 53 58
2015 11 1 3 39 40
2007 9 20 10 49 19
  1 Comment
pruth
pruth on 5 Nov 2015
hey that was so easy...thank u sir....

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More Answers (1)

Thorsten
Thorsten on 5 Nov 2015
Edited: Thorsten on 5 Nov 2015
This works if there is always the string "_L2_" right before the date:
i1 = strfind(filename, '_L2_')+4;
datenum(filename(i1:i1+14),'yyyymmddHHMMSS');

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