MATLAB: What does this syntax mean

syntax;end-364:end;merton;kmv

Can you explain to me what does it mean this syntax end-364:end? Thank you

It looks like it would be inside an array and mean that it's taking the last 365 elements of the array. E.g.

last365elements = data(end-364:end);

That's equivalent to:

[A(1,1), A(1,end);...
 A(1,end), A(end,end)]

Using regexprep, this would be one of the many ways to do it:

a = regexprep(datestr(now, 31), '..(..)-(..)-(..) (..):(..):(..)', '$1$2$3_$4$5$6')

But even simpler, why not ask datestr to output exactly what you want directly:

a = datestr(now, 'yymmdd_HHMMSS')