How to take first three characters of string

Hi,

I have the below cell array:

MA0K123T0
MB0JHY210I9
AoTkU08
880KE21L
PMB456KU0
standard
MF0KET9
twist
MA0KL3
PMV09K

Now I want to filter as below:

If the name start with M or P, then take the first three characters otherwise keep original name. My output should be:

MA0
MB0
AoTkU08
880KE21L
PMB
standard
MF0
twist
MA0
PMV

Answer 1

[Azzi Abdelmalek]

str={'MA0K123T0'
'MB0JHY210I9'
'AoTkU08'
'880KE21L'
'PMB456KU0'}
out=cellfun(@(x) regexprep(x,'\<(M|P).+',x(1:3)),str,'un',0)

[Mekala balaji]

Sir, Thanks Sir. May I ask what is 'un'? and sir, in the same command, If the name start with M or P, then take the alphabets from first three characters otherwise keep original name. My output should be:

MA
MB
AoTkU08
880KE21L
PMB
standard
MF
twist
MA
PMV

[Azzi Abdelmalek]

out=cellfun(@(x) regexprep(x,'\<(M|P).+',regexpi(x,'[a-z]+','match','once')),str,'un',0)

[Guillaume]

@Azzi, cellfun is unnecessary. regexprep works just as well with cell arrays.

@Mekala, 'un', 0 is short for 'UniformOutput', false and tells cellfun to output a cell array. Now that matlab autocompletes the optional argument of cellfun there is no good reason to write 'un', 0.

[Azzi Abdelmalek]

@Gillaume, can you explain how to do it without cellfun?

[Guillaume]

Well, if I were to use regexprep, I'd do it like that:

regexprep(str, '(?<=^[MP]..).*', '')

[Azzi Abdelmalek]

This doesn't give the expected result (look at the new question in the hidden comment)

[Azzi Abdelmalek]

We can use dynamic expressions

match_expr = '(M|P)([a-zA-Z]?)([a-zA-Z]?)(.+)'
replace_expr='$1$2$3'
regexprep(str, match_expr, replace_expr)

Answer 2

[Guillaume]

Azzi's answer with to regex call seems unnecessarily complicated to me. The cellfun is also not required. This simple regex will do:

str = {'MA0K123T0'
       'MB0JHY210I9'
       'AoTkU08'
       '880KE21L'
       'PMB456KU0'}
out = regexp(str, '^[MP].{2}|.*', 'match', 'once')

Which basically says match M or P (the [MP]) at the beginning of the string (the ^) followed by any two characters (the .{2}) and if that does not match, match everything (the &#124.*)

edit for your updated question:

out = regexp(str, '^[MP][A-Za-z]?[A-Za-z]?|.*', 'match', 'once')