Question

i have a cell array as below, which are dates. I am wondering how can i extract the year at the last 4 digits? Could anyone teach me how to locate the year in the string? Thank you!

'31.12.2001'
'31.12.2000'
'31.12.2004'
'31.12.2003'
'31.12.2002'
'31.12.2000'
'31.12.1999'
'31.12.1998'
'31.12.1997'
'31.12.2005'
'31.12.2004'
'31.12.2003'
'31.12.2002'
'31.12.2001'
'31.12.2000'
'31.12.1999'
'31.12.1998'
'31.12.2005'
'31.12.2004'
'31.12.2003'
'31.12.2002'
'31.12.2005'

Answer 1

Example cell array:

A = {'31.12.2001'; '31.12.2002'; '31.12.2003'};

Apply some regular expressions:

B = regexp(A, '\d\d\d\d', 'match')
B = [B{:}];

EDIT: I never realized that matlab will “nest” an extra layer of cells until I tested this. I don’t like this solution as much now that I know the second line is necessary. Here is an alternative approach that gets you the years in numeric form:

C = datevec(A, 'dd.mm.yyyy');
C = C(:, 1);

SECOND EDIT: Suprisingly, if your cell array has less than 10000 elements, the regexp approach is faster on my machine. But the output of it is another cell array (which takes up much more memory than a numeric matrix). You can use B = cell2mat(B) to get a character array instead, but this brings the two approaches to approximately equal efficiency.