stelios loizidis asked . 2023-04-17

Select values based on datetime

Hello,

I have the matrix Values (1X2100) and the corresponding DateTime matrix with datetime data (1x2100 datetime). The values in Values matrix are hourly. I want to categorize the values of the Values table into 3 categories. I wrote the following codes for categorization,

[k1,i1]=find(Values<0);
[k2,i2]=find(0<=Values & Values<=80;
[k3,i3]=find(80<Values);

Based on the i1, i2 and i3 I created the following matrices,

Cat_Time_1=DateTime(i1);
Cat_Time_2=DateTime(i2);
Cat_Time_3=DateTime(i3);

Cat_Time_1 (1X30 datetime), Cat_Time_2 (1X290 datetime) and cat_Time_3 (1X1780 datetime)

But what happens is the following: For example, in Cat_Time_1 there is 04-Jan-2012 04:00 and in Cat_Time_2 there is 04-Jan-2012 16:00. Another example is in Cat_Time_2 there is 16-Jan-2012 07:00 and in Cat_Time_3 there is the 16-Jan-2012 02:00. What I want is the same dates that exist in Cat_Time_1 and Cat_Time_2 stay in Cat_Time_1 and leave Cat_Time_2. The same dates that exist in Cat_Time_1 and Cat_Time_3 should leave from cat_Time_3 and stay in Cat_Time_1, while the same dates that exist in Cat_time_2 and Cat_Time_3 should leave Cat_Time_2 and stay in Cat_Time_3.

After that, based on the dates that exist in each matrix (Cat_Time_1, Cat_Time_2 and Cat_Time_3), all the values must be selected from the Values matrix of prices that correspond to the date. (e.g. in Cat_Time_1 the first date is 04-Jan-2012. The first row of the cat1 matrix should contain the 24 values corresponding to this date. The same in the other cases). How are these done?

matrix , datetime ,

Expert Answer

Kshitij Singh answered . 2024-12-21 02:44:54

The very first thing you should do is put your data and timestamps in a timetable.

Once you do that, use retime to create a daily timetable, using your own custom aggregation function that returns 1, 2, or 3 according to your rules ("the same dates that exist in Cat_Time_1 and Cat_Time_2 stay in Cat_Time_1 and leave Cat_Time_2 ...", which I don't really understand but you should be able to write that function.

Now you have a list of days and what category they are in. Use dateshift on your original timetable to add a new variable that is the day timetamp, use join to combine that with the daily timetable, and select data from tyhat using the category number.

The custom function aside, this is just a few lines of code. No loops needed.

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