read date from character string

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.

Answer 1

[Stephen23]

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

[pruth]

hey that was so easy...thank u sir....

Answer 2

[Thorsten]

This works if there is always the string "_L2_" right before the date:

 i1 = strfind(filename, '_L2_')+4;
 datenum(filename(i1:i1+14),'yyyymmddHHMMSS');