search interval in datetime

hi, I have a datetime array of several many days. I need to serch interval

example:

TimeA=22:00

TimeB=03:00

search datetime>=timeA and datetime<=timeB (22:00 ..22:01..22:02. etc......23:59 ..00:00...00:01.etc... 2:58..2:59 3:00)

So I want without checking the day to have the indices of that range in the whole array

(the times in datetime are already ordered in a correct chronological way so the next time is always after the previous one)

Answer 1

[Steven Lord]

Use the timeofday function to return the time since midnight of each element of the datetime array.

T = datetime('today') + hours(24*rand(10, 1))

T = 10x1 datetime array
   21-May-2024 00:01:16
   21-May-2024 10:22:46
   21-May-2024 07:40:50
   21-May-2024 23:22:42
   21-May-2024 10:42:10
   21-May-2024 20:30:07
   21-May-2024 22:42:34
   21-May-2024 13:15:17
   21-May-2024 06:45:24
   21-May-2024 06:13:04

TOD = timeofday(T)

TOD = 10x1 duration array
   00:01:16
   10:22:46
   07:40:50
   23:22:42
   10:42:10
   20:30:07
   22:42:34
   13:15:17
   06:45:24
   06:13:04

Then compare to duration objects representing the ends of the interval of interest. In this case because the interval includes midnight we need to ask if the timeofday is greater than the first end or less than the second end.

past2200 = TOD > duration(22, 0, 0)

past2200 = 10x1 logical array
   0
   0
   0
   1
   0
   0
   1
   0
   0
   0

before0300 = TOD < duration(3, 0, 0)

before0300 = 10x1 logical array
   1
   0
   0
   0
   0
   0
   0
   0
   0
   0

T(past2200 | before0300)

ans = 3x1 datetime array
   21-May-2024 00:01:16
   21-May-2024 23:22:42
   21-May-2024 22:42:34

results = table(T, past2200, before0300, past2200 | before0300, ...
    'VariableNames', ["times", "> 2200", "< 0300", "overnight"])

results = 10x4 table
           times            > 2200    < 0300    overnight
    ____________________    ______    ______    _________

    21-May-2024 00:01:16    false     true        true   
    21-May-2024 10:22:46    false     false       false  
    21-May-2024 07:40:50    false     false       false  
    21-May-2024 23:22:42    true      false       true   
    21-May-2024 10:42:10    false     false       false  
    21-May-2024 20:30:07    false     false       false  
    21-May-2024 22:42:34    true      false       true   
    21-May-2024 13:15:17    false     false       false  
    21-May-2024 06:45:24    false     false       false  
    21-May-2024 06:13:04    false     false       false  

[Luca Re]

Good ..

and another question:

I want to search with a lot of condition:

Exampe:

1)TimeA=22:00 and TimeB=03:00

2)Year from 2008 to 2010 (A B)

3)month from 1 to 3 (C D)

4)day from 5 to 10 (E F)

I do it but using this procedure:

%Calculate Interval Year !

[a]=find(year(dat)>=A,1,'first');

[b]=find(year(dat)<=B,1,'last');

idxx=a:b; % ===> valid indices

%Calculate Interval Month !

a1=find(month(dat)>=C & month(dat)>=D);

%Calculate Interval Dayy. !

.....

a=ismember(a1,idxx);

idxx(a)=[];

idxx contains valid indexes...

but can you code using queries in a simpler way?

[Steven Lord]

Use the ymd function to obtain the year, month, and day components of the datetime.

dt = datetime('now')

dt = datetime
   21-May-2024 15:02:57

[y, m, d] = ymd(dt)

y = 2024

m = 5

d = 21

There's a similar hms function for hour, minute, and second.

[h, m2, s] = hms(dt)

h = 15

m2 = 2

s = 57.0178

[Luca Re]

oky thank