Problem in finding correct date.

I am writting a code to see whether a particular date is valid or not. The function takes three positive integer scalar inputs. If it is a valid date it returns true or else false.

When I try to use the following code in the command window

valid = valid_date(2018,4,1)
valid = valid_date(2018,4,31)

It returns false for both the cases. However it should return true for the first case and false for the second case.

My code is as follows

function valid =  valid_date(year,month,day)
if ~isscalar(year) ||~isscalar(month) || ~isscalar(day);

valid = false;
 
else

valid = true;

end

if year<1 || month<1 || day<1;

valid = false;
else 
    valid = true;
end

if month==4||month==6||month==9||month==11 && day<=30
 valid = true;
else 
    valid = false;
end
 if month==1||month==3||month==5||month==7||month==8||month==10||month==12 && day<=31
 valid = true;
 
else
    valid = false;
  
end

[Om Yadav]

Your if else is creating problem. You assigning 0 or 1 in each if condition. Ultimately, only last assigment survives. Let me give you an example of this. You just put your month==4 condition in the end and you will get the answer correct for months 4,6,9,11 and incorrect for others.

Suggestion is, only give condition and assignment. And else in the last loop like

function valid = valid_date(year,month,day)

if ~isscalar(year) ||~isscalar(month) || ~isscalar(day)

valid = false;

end

if year<1 || month<1 || day<1

valid = false;

end

if (month==1||month==3||month==5||month==7||month==8||month==10||month==12) && day<=31

valid = true;

end

if (month==4||month==6||month==9||month==11) && day<=30

valid = true;

else

valid=false;

end

But again Feb is problem so I am highlighting where you are faulting.

Answer 1

[Ameer Hamza]

Try this simpler version

function tf = valid_date(y, m, d)
    [Y,M,D] = ymd(datetime(y, m, d));
    tf = all([Y M D] == [y m d]);
end

Result

>> valid_date(2018,4,1)
ans =
  logical
   1
>> valid_date(2018,4,31)
ans =
  logical
   0

Answer 2

[Kulko Margarita]

function isvalid = valid_date(y, m, d)
   % Check if the inputs are valid 
   % Check that they are scalars
   if ~(isscalar(y) && isscalar(m) && isscalar(d))
       isvalid = false;
   % Check that inputs are positive
   elseif ~all([y, m, d] > 0)
       isvalid = false;
   % Check that inputs are integers (not the data type)    
   elseif any(rem([y, m, d], 1))
       isvalid = false;
   % Check that m and d are below the max possible
   elseif (m > 12) || (d > 31)
       isvalid = false;
   % The inputs could be a valid date, let's see if they actually are
   else
       % Vector of the number of days for each month
       daysInMonth = [31 28 31 30 31 30 31 31 30 31 30 31];
       % If leap year, change days in Feb
       if isequal(rem(y, 4), 0) && (~isequal(rem(y, 100), 0) || isequal(rem(y, 400), 0))
            daysInMonth(2) = 29;
       end
       maxDay = daysInMonth(m);
       if d > maxDay
           isvalid = false;
       else
           isvalid = true;
       end
       
   end
end