How to optimize a code to find postfix in a sting

Hi! 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, can you help me to find the error Thanks

[Stephen23]

You should try using my FEX submission make_regexp:

http://www.mathworks.com/matlabcentral/fileexchange/48930-regular-expression-helper

This creates a figure which lets you interactively create regular expressions, and alter them while it shows you the regexp outputs. It lets you change your regular expressions and immediately see what effect it has on the string matching.

[pamela sulis]

I have some problems to understand the code: I'm not very expert about matlab :(

Answer 1

[Walter Roberson]

matches(k) = regexp(TrajCompact(k), '(?<=\(?[0-4]{2}).*', 'match', 'once');

this would strip off an optional '(' followed by a single two-digit number that is composed of the digits 0-4 only, and the rest of the string would be returned.

If this is not what you want please post a sample input line.

Answer 2

[Stephen23]

Your first regular expression has a backslash, but your sprint version does not. The first regular expression:

>> '\(?00.*'
ans = \(?00.*

The second regular expression:

>> sprintf('?%d%d.*', 0, 0)
ans = ?00.*

The strings look quite different to me. Perhaps you wanted this:

>> sprintf('\\(?%d%d.*', 0, 0)
ans = \(?00.*