Problem when creating a datetime array using reference and sampling frequency

Hello,

I am trying to create a datetime array that begins with a starting datetime (st) I've set and which increases with respect to a sampling frequency (fs). To do that I'm running this code

t=[];                                                 
t=st;                                                 
for i=2:length(time)                                  
   t(i)=t(i-1)+seconds(1/fs);
end

However, it seems that the program is stuck in an inifite loop. When running the loop step by step, it works fine.

I've also tried this:

t=[];                                                                                                
for i=1:length(time)                                  
  t=[t;st+ seconds(i/fs)];
end

But it still doesn't work.

Answer 1

[Steven Lord]

It's going to be difficult to know why your code appears to run infinitely without knowing the contents of st, time, and fs. But if you know the start time, end time, and increment you want your vector to have, don't use a for loop (especially not one in which you grow the t array by one element each iteration!) Instead use the colon operator.

startTime = datetime('now');
endTime = startTime + days(1);
inc = hours(1);
V = startTime:inc:endTime;

This counts from right now to this time tomorrow in increments of 1 hour.

Answer 2

[yanis]

Thanks for you answer. So st is basically a date time variable corresponding to when my data started to be acquired.

I want the program to count from that starting point with increments in seconds of 1/fs where fs is a sampling frequency of 125 Hz.

[Peter Perkins]

Following up on essentially the same idea that Steve suggested:

>> st = datetime(2018,8,3,16,0,0,'Format','dd-MMM-yyyy HH:mm:ss.SSS')
st = 
  datetime
   03-Aug-2018 16:00:00.000
>> n = 10;
>> t = st + seconds((0:n-1)/125)
t = 
  1×10 datetime array
Columns 1 through 5
   03-Aug-2018 16:00:00.000   03-Aug-2018 16:00:00.008   03-Aug-2018 16:00:00.016   03-Aug-2018 16:00:00.024   03-Aug-2018 16:00:00.032
Columns 6 through 10
   03-Aug-2018 16:00:00.040   03-Aug-2018 16:00:00.048   03-Aug-2018 16:00:00.056   03-Aug-2018 16:00:00.064   03-Aug-2018 16:00:00.072