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How can I interpolate a datetime data series to have an interval of 1 minute in MATLAB?

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James
James on 30 Dec 2020
Commented: Ameer Hamza on 30 Dec 2020
Hi everyone,
I'm analyzing a sample dataset from a .csv file (Attached). The columns are: "Ref number, MMSI, Latitude, Longitude, Timestamp (DateTime), Speed, Course". But the data is not consistent with time and, the interval between data points is not the same. Also, the data have to be grouped by the MMSI (the ID). So each ID has a set of data points but they have different time intervals.
How can I take each group of data and check their consistency, and then interpolate all the data such that, the time interval between two consecutive data points is one minute?
What I want to achieve is basically:
Data should be grouped based on MMSI - which is basically the ID. (Thanks to this community, I can get this part done without a problem)
Each group should have a consistent data series (of Latitude, Longitude, Timestamp (DateTime), Speed, Course) with a time interval of one minute between two points.
How can I approach this?

Accepted Answer

Ameer Hamza
Ameer Hamza on 30 Dec 2020
Try something like this
T = readtable('sample.xlsx');
[grps, unique_mmsi] = findgroups(T.mmsi);
tts = splitapply(@(la,lo,da,so,co) {timetable(da, [la lo so co])}, T(:,3:end), grps);
out = cellfun(@(tt) retime(tt, 'minutely'), tts, 'uni', 0)
The issue here is that some rows having the same mmsi have duplicate timestamps with slightly different data values. This prevents linear interpolation. For example, check row 295 and 296.
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