Match return substring between two substrings using regexp

Question

I have a list of records that are character vectors. Here's an example:

'1mil_0,1_1_1_lb200_ks_drivers_sorted.csv'
'1mil_0_1_lb100_ks_drivers_sorted.csv'
'1mil_1_1_lb2_100_100_ks_drivers_sorted.csv'
'1mil_1_1_lb100_ks_drivers_sorted.csv'

From these names I would like to extract whatever's between the two substrings 1mil_ and _ks_drivers_sorted.csv.

So in this case the output would be:

0,1_1_1_lb200
0_1_lb100
1_1_lb2_100_100
1_1_lb100

I'm using MATLAB so I thought to use regexp to do this, but I can't understand what kind of regular expression would be correct.

Or are there some other ways to do this without using regexp?

1mil_(.*)_ks_drivers_sorted\.csv and use captured group #1 — anubhava
– anubhava, Commented Sep 8, 2017 at 13:45

Luis Mendo · Accepted Answer · 2017-09-08 16:28:03Z

4

Let the data be:

x = {'1mil_0,1_1_1_lb200_ks_drivers_sorted.csv'
     '1mil_0_1_lb100_ks_drivers_sorted.csv'
     '1mil_1_1_lb2_100_100_ks_drivers_sorted.csv'
     '1mil_1_1_lb100_ks_drivers_sorted.csv'};

You can use lookbehind and lookahead to find the two limiting substrings, and match everything in between:

result = cellfun(@(c) regexp(c, '(?<=1mil_).*(?=_ks_drivers_sorted\.csv)', 'match'), x);

Or, since the regular expression only produces one match, the following simpler alternative can be used (thanks @excaza for noticing):

result = regexp(x, '(?<=1mil_).*(?=_ks_drivers_sorted\.csv)', 'match', 'once');

In your example, either of the above gives

result =
  4×1 cell array
    '0,1_1_1_lb200'
    '0_1_lb100'
    '1_1_lb2_100_100'
    '1_1_lb100'

edited Sep 8, 2017 at 16:28

answered Sep 8, 2017 at 13:49

Luis Mendo

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5 Comments

jackscorrow Over a year ago

Exactly what I needed. Thank you!

Sardar Usama Over a year ago

result = regexp(x, '(?<=1mil_).*(?=_ks_drivers_sorted.csv)','match'); [result{:}].' (if you want to avoid cellfun)

Luis Mendo Over a year ago

@SardarUsama Good idea. But I'm not sure that result = [result{:}].' is much clearer than result = cellfun(@(c) ..., x)

Sardar Usama Over a year ago

I agree with that though :)

sco1 Over a year ago

@SardarUsama If you use regexp with 'once' you don't need to denest the cells.

Yiao SUN · Accepted Answer · 2017-09-08 14:07:15Z

0

For me the easy way to do this is just use espace or nothing to replace what you don't need in your string, and the rest is what you need.

If is a list, you can use a loop to do this.

Exemple to replace "1mil_" with "" and "_ks_drivers_sorted.csv" with ""

newChr = strrep(chr,'1mil_','')
newChr = strrep(chr,'_ks_drivers_sorted.csv','')

answered Sep 8, 2017 at 14:07

Yiao SUN

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