How to set regexp expression for HH:MM format?

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Hy, I have a gui where i want to check the user input dateSTOP for the format. The format should be in this order HH:MM with all the characters used (eg 02:03 01.03.2014 not 2:3 1:3.14). I use this code...
control = regexp(dateSTOP,'[012][0-9]:[0-6][0-9] [1-9]|([012][0-9])|(3[01])).([0][1-9]|1[012]).\d\d\d\d')
errordlg('Use format: 05:00 04.09.2014','modal'));
but that also allows the short version. How to rewrite the regexp expression to have all characters?

Accepted Answer

Joachim Schlosser
Joachim Schlosser on 17 Oct 2014
There is a function that does the parsing for you.
t = datetime(dateSTOP,'InputFormat','hh:mm dd.MM.yyyy')
doc datetime
sejo on 18 Oct 2014
Thx for brining up this function! didnt know about that... there are so many that sometimes its hard to find the perfect one.

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More Answers (2)

Guillaume on 17 Oct 2014
First, from a user interface perspective, why don't you want to allow 2:3 1:3:14? In my opinion, user convenience should trump programmer convenience, so make it easy for the user to enter the date even if it's harder to check. You write the code only once, the user uses it numerous time.
Secondly, I wouldn't use a regexp to validate the date. You can do it, but it's going to be a very complicated one. For example, your regexp (once corrected) would still allow abcef 29:69 31.02.9999 ijk. So, what I would do is use a regular expression to extract the numbers and just basic checks and validate the date the traditional way with if tests:
n = regexp(dateStop, '^(\d+):(\d+) (\d+)\.(\d+)\.(\d+)$', 'tokens', 'once'); %just validate it's numbers with right separators and extract numbers
if isempty(n)
error('invalid date');
n = num2cell(str2double(n)); %convert strings to numbers and stuff into cell array to distribute on next line
[hour, minute, day, month, year] = n{:}; %distribute cell array to named variables for convenience
if hour < 1 || hour > 23 || minute < 1 || minute > 59 || day < 1 || month < 1 || month > 12 || year < 1
error('invalid date');
if (ismember(month, [1 3 5 7 8 10 12]) && day > 31) || (ismember(month, [4 6 9 11]) && day > 30) || (month == 2 && day > 28) %potentially also allow for leap years and add test
error(invalid date');
Anyway, with regards to your regular expression, you've misplaced some brackets. Note that the | operator in a regexp take into account the entirety of the expression before and after. Therefore your regular expression allowed '[012][0-9]:[0-6][0-9] [1-9]' or '[012][0-9]' or ... It's both alternative with the operator that you need to enclose in brackets, not each one. Additionally, you seem to be allowing a day that is a single digit. Also, you need to escape the . otherwise they match any characters
The correct regexp would be:
control = regexp(dateSTOP,'[012][0-9]:[0-6][0-9] ([012][0-9]|3[01])\.([0][1-9]|1[012])\.\d\d\d\d')
if isempty(control)
But as mentioned, this regexp allows abcef 29:69 31.02.9999 ijk. You can eliminate the allowed extra characters by anchoring your regexp (with ^ and $) but to reproduce my two ifs you need:
control = regexp(dateSOP, '^([01][0-9]|2[0-3]):[0-5][0-9] ((([012][0-9]|3[01])\.(01|03|05|07|08|10|12))|(([012][0-9]|30)\.(04|06|09|11))|(([01][0-9]|2[0-8])\.02)\.\d{4}$'); %untested
Guillaume on 17 Oct 2014
My first example allows short input and give you hours, minutes, day, month and year. That is easily converted into a datevec, datenum, datetime, datestr, or whatever else you want, e.g:
dn = datenum([year month day hour minute 0]);

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Matt Tearle
Matt Tearle on 17 Oct 2014
As an alternative suggestion, one approach is to pass the problem on to datenum: just pass the user's input along to datenum and see if datenum can handle it. If it fails, then the input wasn't OK.
% see what datenum does with the input
dateSTOPnum = datenum(dateSTOP,myFormat);
% failure => bad input
errordlg('Use format: 05:00 04.09.2014','modal'));
Matt Tearle
Matt Tearle on 17 Oct 2014
You can check for that by converting the datenum back to a datestr (with the same format specification), and comparing to the original string.

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