Creating index from datetime vector days

Hi,

I have a 100x1 datetime vector. I have extracted the values of the day using the ymd function: [~,~,d] = ymd(input).

How can I create a vector with a unique identifier for every period from the 15th to the 14th in the days vector, d (each sequence of 15 to the next 14). (i.e. from jan 15 - feb 14, i could have 1's, from feb 15 - mar 14, i can have 2s, etc.)

Any help would be appreciated. Thx in advance!

DB

Answer 1

[Walter Roberson]

Take the month number output as well as the day output. If the day is less than 15, subtract 1 from the month number to get the index (if the month number was 1, substitute 12 for previous year); otherwise use the month number directly.

[dan berkowitz]

Works like a charm! Thank you! DB

Answer 2

[Peter Perkins]

discretize does this for you:

>> dt = datetime(2017,1,1:10:100)'
dt = 
  10×1 datetime array
   01-Jan-2017
   11-Jan-2017
   21-Jan-2017
   31-Jan-2017
   10-Feb-2017
   20-Feb-2017
   02-Mar-2017
   12-Mar-2017
   22-Mar-2017
   01-Apr-2017
>> edges = datetime(2016,12,15) + calmonths(0:5)
edges = 
  1×6 datetime array
   15-Dec-2016   15-Jan-2017   15-Feb-2017   15-Mar-2017   15-Apr-2017   15-May-2017
>> discretize(dt,edges,'categorical')
ans = 
  10×1 categorical array
     [15-Dec-2016, 15-Jan-2017) 
     [15-Dec-2016, 15-Jan-2017) 
     [15-Jan-2017, 15-Feb-2017) 
     [15-Jan-2017, 15-Feb-2017) 
     [15-Jan-2017, 15-Feb-2017) 
     [15-Feb-2017, 15-Mar-2017) 
     [15-Feb-2017, 15-Mar-2017) 
     [15-Feb-2017, 15-Mar-2017) 
     [15-Mar-2017, 15-Apr-2017) 
     [15-Mar-2017, 15-Apr-2017)

If you really need numbers for the bins, just leave off the 'categorical' flag.