Selecting specific values in timestamp

Hello,

I have a 7000000x8 matrix. In the second column, I have the timestamp information (e.g.: 11/02/2020 14:19:34.000). My sampling frequency is 25 Hz. In the 7th column I have temperature data. The timestamp column has continuous data for 4 consequetive days. How can I select the temperature data on 12/02/2020 14:00:00.000 until 12/02/2020 15:30:00.000? Or how can I find the indices of a specific timestamp in order to retrieve the temperature data?

Thank you.

Answer 1

[Sai Sri Pathuri]

Assuming you have a

• Table t of size 7000000x8 with column names timestamp and temperature for timestamp (2nd column) and temperatue (4th column) data respectively. You may find the indices containing the required timestamps as below

          first_index = find(ismember(t.timestamp,'12/02/2020 14:00:00.000','rows')) 
          last_index  = find(ismember(t.timestamp,'12/02/20201 5:30:00.000','rows')) 

Now temperature data can be obtained from these indices

          temperatureData = t.temperature(first_index:last_index) 

• Cell array c of size 7000000x8. You may find the indices containing the required timestamps as below. Note that ‘2’ is the column containing timestamp values

          first_index = find(ismember(c(:,2),'12/02/2020 14:00:00.000')) 
          last_index  = find(ismember(c(:,2),'12/02/20201 5:30:00.000')) 

Now temperature data (column = ‘4’) can be obtained from these indices.

          temperatureData = c(first_index:last_index,4)