Filtering sequences in MATLAB -

is possible regular expressions matlab filter things out? i'm looking let me take vector like:

[1 2 1 1 1 2 1 3 3 3 3 1 1 4 4 4 1 1] 

and return:

[3 3 3 3 4 4 4] 

these uninterrupted sequences (where there's no interspersion).

is possible?

using regular expressions

use matlab's built-in regexp function regular expression matching. however, have convert input array string first, , feed regexp:

c = regexp(sprintf('%d ', x), '(.+ )(\1)+', 'match') 

note separated values spaces regexp can match multiple digit numbers well. convert result numerical array:

res = str2num([c{:}]) 

the dot (.) in pattern string represents character. find sequences of digits only, specify them in brackets ([]). instance, pattern find sequences of 3 , 4 be:

([34]+ )(\1)+ 

a simpler approach

you can filter out successively repeating values checking similarity between adjacent elements using diff:

res = x((diff([nan; x(:)])' == 0) | (diff([x(:); nan])' == 0)) 

optionally, can keep values result, example:

res(res == 3 | res == 4)