Generate timestamp series in Matlab? - matlab

Question

all
I wonder if there is a way to generate timestamp series in Matlab ?
I assume there will be a start time, a end time, and a frequency.
It is simple to generate normal series using 1:1:100 (1 to 100 by 1)
How I can use a similar way to generate a time stamp series?
For instance, I specify start time as 9am, up to 10am, I want to generate something like 9:00:00:000, 9:00:00:500, 9:00:01:000, ....
gaped by 500 millisecond
Or even better, include date as well.

Answer 1

Use datenum, the only problem you might have is that your colliding with a gap second/day or summer savings time if you're spanning a long time period (but I don't think that's implemented in datestr as you can read here).
Play around with datenum, now and datestr
starttime = datenum(2000, 1, 1, 9, 0, 0);
dt = 0.500/86400; % datenum is a serial time format with 1 = 1 day = 86400 sec
N = 5;
timevec = starttime + dt*(0:(N-1));
>> datestr(timevec, 'HH:MM:SS.FFF')
ans =
09:00:00.000
09:00:00.500
09:00:01.000
09:00:01.500
09:00:02.000

Answer 2

Starting from 2015a, you can use the milliseconds function to build a vector of timesteps between to time points:
start = datetime('2017/1/3 9:00:00:000','InputFormat','yyyy/MM/dd H:mm:ss:SSS');
step = milliseconds(500);
fin = datetime('2017/1/3 10:00:00:000','InputFormat','yyyy/MM/dd H:mm:ss:SSS');
time_vec = start:step:fin;
If you don't define the date explicitly it will choose the current date.
You can also have one structure for both the time and the data, you can use the timeseries class (using start from above):
data = rand(7201,1);
ts = timeseries(data,'Name','MyTs');
ts.TimeInfo.StartDate = start;
ts.TimeInfo.Units = 'milliseconds';
ts = setuniformtime(ts,'Interval',500);
This will create a time series object:
>> ts
timeseries
Common Properties:
Name: 'MyTs'
Time: [7201x1 double]
TimeInfo: [1x1 tsdata.timemetadata]
Data: [7201x1 double]
DataInfo: [1x1 tsdata.datametadata]
with the following time info:
>> ts.TimeInfo
tsdata.timemetadata
Package: tsdata
Uniform Time:
Length 7201
Increment 500 milliseconds
Time Range:
Start 03-Jan-2017 09:00:00
End 03-Jan-2017 10:00:00
Common Properties:
Units: 'milliseconds'
Format: ''
StartDate: '03-Jan-2017 09:00:00'

Answer 3

It depends on your needs, but you can consider using the combination of datetime() and one or many of days(), hours(), minutes(), seconds() etc. functions.
Lets write some code:
start=datetime(1985,07,13,9,0,0); % your start date
steps=seconds(0:0.5:100); % your vector with steps
timeseries=start+steps; % your time series
you can also set format for displaying data that meets your needs, to do so check datetime properties manual.