How to find the day number of any year from a date?

I am very new in programming and therefore it is probably a novice's question. I have to write a script that takes a number of day(dd), month(mm) and year(yyyy)values arranged in three separate columns of a MATLAB variable and gives the day number of the year(e.g. for 03 March 2012, 31+29+3=63) as output.

[Azzi Abdelmalek]

Can you explain?

[Md. Golam Mostafa]

I have a variable in the workspace containing all the data. Column 1 stores the day(dd), column 2 month (mm) and column 3 year (yyyy). I need to find the day number (for example, for 02/01/2012 day number=2, for 03/03/2012 day number=Jan (31)+ Feb (29)+ Mar (03)=63). The day number is 63. But for 03/03/2013 day number=Jan (31)+ Feb (28)+ Mar (03)=62). I need output of each date in a separate variable.

Answer 1

[Peter Perkins]

If you are using R2014b or later, the datetime data type allows you to compute the day of year using the day function:

>> x = [2012 1 2; 2012 3 3; 2013 3 3]
x =
        2012           1           2
        2012           3           3
        2013           3           3
>> d = datetime(x)
d = 
   02-Jan-2012
   03-Mar-2012
   03-Mar-2013
>> day(d,'dayofyear')
ans =
     2
    63
    62

[Md. Golam Mostafa]

I am running this code but it shows an error of this kind.

??? Undefined function or method 'datetime' for input arguments of type 'double'.

Error in ==> testdaynum1 at 32 d = datetime(YMD);

What is the solution?

[Peter Perkins]

Presumably, you are not "using R2014b or later". datetime did not exist prior to that.

Answer 2

[Andrei Bobrov]

x = [2012 1 2; 2012 3 3; 2013 3 3];

d = datenum(x);
out = d - datenum(year(d),1,1) + 1;

Answer 3

[Jos (10584)]

help datenum

and then use simple subtraction

Answer 4

[Sergey Kostrukov]

Fractional value of days since biginning of the year (0-364.9999):

daysFrac = days(currentTime - datetime(year(currentTime), 1, 1, TimeZone=currentTime.TimeZone))

To get the whole number starting from 1 (i.e. day index):

floor(daysFrac + 1)