doydocumentation
Thedoyfunction returns the Julian day of year.
See alsoday.
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Contents
Syntax
机灵机灵n = (t) n = (t)的分malyear') n = doy(t,'remdecimalyear')
Description
n = doy(t) gives the day of year (from 1 to 366.999) corresponding to the date(s) given by t. Input dates can be datenum, datetime, or string format.
n = doy(t,'decimalyear') gives the year in decimal form of input date t. It accounts for leap years, so the decimal value for a given date will depend on whether it's a leap year. For example, July 4th of 2016 (a leap year) is 2016.5082 whereas July 4th of 2017 (not a leap year) is 2017.5068.
n = doy(t,'remdecimalyear') returns only the remainder of the decimal year, and is always in the range 0 to 1.
Example 1:datestrformat
What's the Julian day of the year for Valentine's Day?
doy('february 14')
ans = 45.00
45. That's because there are 31 days in January, and Valentine's Day is on the 14th of February.
Example 2:datenumformat
As I write this example file, it is
>>now ans = 737427.95
which means it has been 737427 days since January first of the year zero. So what day of the year is it right now?
doy(737427.95)
ans = 2.95
As you can see, it is late at night on January 2nd. Only 5% of the day remains.
Example 3:datetimeformat
Consider this sea ice extent data:
loadseaice_extent.matwhosextent_Nt% displays sizes of these variables
Name Size Bytes Class Attributes extent_N 12854x1 102832 double t 12854x1 205665 datetime
The variabletis indatetimeformat, and it contains one date just about every from 1978 to 2018. Here's the time series:
情节(t, extent_N) ylabel'sea ice extent (10^6 km^2)'boxoff% removes the ugly frame
Plot the data as a function of Julian day like this
jday = doy(t); scatter(jday,extent_N,10,datenum(t),'filled') cb = cbdate('yyyy');% formats the colorbar as datesset(cb,'ydir','reverse')% flips the colorbar axisaxistightylabel'northern hemisphere sea ice extent (10^6 km^2)'xlabel'day of year'
Author Info
This function is part of theClimate Data Toolbox for Matlab. The function and supporting documentation were written by Chad A. Greene of the University of Texas at Austin.