Write a function to extracts number between 2 letters?

I am trying to write a MATLAB code that extracts a 3 digit number in between two letters. the tricky part is that the letter after the number could be either (s)or(h)

E.g 1 the filename is 'rfc_f123sars.tif' this should extract 123 which is between _f and s E.g 2 the filename is 'rfc_f456hars.tif' this should extract 456 which is between _f and h Thanks :)

Answer 1

[per isakson]

Without comments

>> str =  'rfc_f123sars.tif' ;
>> regexp( str, '(?<=_f)\d{3}(?=[sh]{1})', 'match', 'once' )
ans =
123

and slightly different; replace [sh]{1} by (s|h), which is a tiny bit cleaner

>> str = 'rfc_f456hars.tif';
>> regexp( str, '(?<=_f)\d{3}(?=(s|h))', 'match', 'once' )
ans =
456

If regexp returns empty set out=0

[Walter Roberson]

I think you mean [sh] rather than [so]

[per isakson]

Thanks! Yes, indeed. I picked the "o" in "or" and tested with "s" :-)

[Mohammed]

thank you :) :)

[Guillaume]

Note that [sh]{1} is exactly the same as [sh]

Answer 2

[Walter Roberson]

regexp(filename, '\d\d\d', 'match')

or if you want to be more secure,

regexp(filename, '(?<=[A-Za-z])\d\d\d(?=[A-Za-z])', 'match')

[Mohammed]

Thanks Walter:)

Answer 3

[Guillaume]

This is trivial with a regular expression:

nstr = regexp(filename, '(?<=_f)\d+(?=(s|h))', 'match', 'once');
if isempty(nstr)
   n = 0;
else
   n = str2double(nstr);
end

The regular expression matches a sequence of one or more digit, preceded by _f, followed by h or s.

[Mohammed]

Thank you Guillaume!