Matlab: how to optimize a code to find postfix in a sting

Question

I have a cell 106x1 of strings TrajCompact . In every string I want to find all the prefix that are combination of (0,1,2,3,4) and consider only the postfix after this prefix My prefix are:

00,01,02,03,04,10,11,12,13,14,20,21,22,23,24,30,31,32,33,34,40,41,42,43,44

I try to do this, using the code

for k=1:size(TrajCompact,1)
    matches(k) = regexp(TrajCompact(k), '\(?00.*', 'match', 'once');
end

The code run but I have to write it 25 times: one for every prefix. I want to find a compact expression so I modify the code in this way:

[digits{1:2}] = ndgrid(0:4);
for k=1:106
    matches(k) = regexp(TrajCompact(k), sprintf('?%d%d.*', digits{1}(k), digits{2}(k)), 'match', 'once');
end

but it doesn't make what I want, what is the flaw here?

Answer 1

You should solve the problem inside the regexp :

matches{k} = regexp(TrajCompact{k}, '\(?[0-4][0-4].*', 'match', 'once');

Later Edit

Based on a longer discussion in the comments of this post, the solution for OPs problem should lie along the lines of using the function:

get_matches = @(x,c)cellfun(@(s)regexp(s,sprintf('\\(%s\\)[0-4]+',x),'match'),c,'UniformOutput',false);

For example, for the string cell:

str_cell = {'(23)2' '02(13)(23)1(23)21(23)20(23)1(23)21(23)1(23)(13)(23)1(32)31(32)12321(23)21321(23)132(31)(32)31(32)12321(23)21(23)21(23)20(23)2' '210432342432132342(34)323134(32)43413243424321234321432412343212(34)1341234' '24321(34)(32)3432134(32)3431(34)323432(34)(32)3432(34)3'};

the matched strings may be retrieved as:

a23 = get_matches('23', str_cell);
a23 = [a23{:}];

Looping over possible "prefixes" is trivial.