It depends on how you would like to split the input. As entered, your expression evaluates to
>> test = regexpi('string','\x','split')
test =
cell
'string'
The metacharacter '\x' is used if you have the hexadecimal value of a desired character that you want to match. For all the metacharacters, see:
If you wanted to split an arbitrary string anywhere that it had a certain hexadecimal character, then you would have to specify the hexadecimal value after '\x'. For example
% ASCII hex value for character for 'i' is 69
>> test = regexpi('string','\x69','split')
test =
1×2 cell array
'str' 'ng'
To recover the hex value for a given character, you could use dec2hex
>> dec2hex('i')
ans =
'69'
