How can I find out some specific dates from two date lists?

Hi, I have two date lists. DateList1.m contains dates from 1984 to 2022 (with many gaps) and DateList2.m constains dates from 2005 to 2019 (with no gap). I want to make a table that contains all temperature data between 9:00 am to 11:00 am from DateList2.m but those specific dates need to be in dateList1.m as well.

Can anyone please suggest how to code this problem? Any feedback will be much appreciated!

Answer 1

[Cris LaPierre]

You have date information in DateList1, and date+time information in DateList2.

I would add a column to DateList2 that is just the date. You might find the dateshift function helpful for this. Then I could use ismember to find which dates in DateList2 are in DateList1. At the sime time, you could check that the day time is between 9 and 11 am. Use the hour function with the corresponding relational operators.

[Cris LaPierre]

This is what I was thinking

load DateList1.mat
load DateList2.mat

DateList2.date = dateshift(DateList2.Time, 'start', 'day')

DateList2 = 525881×2 timetable
            Time            Var1       date    
    ____________________    ____    ___________

    01-Jan-2005 00:00:00    5.34    01-Jan-2005
    01-Jan-2005 00:15:00     5.3    01-Jan-2005
    01-Jan-2005 00:30:00    5.27    01-Jan-2005
    01-Jan-2005 00:45:00     5.3    01-Jan-2005
    01-Jan-2005 01:00:00    5.41    01-Jan-2005
    01-Jan-2005 01:15:00    5.87    01-Jan-2005
    01-Jan-2005 01:30:00    5.57    01-Jan-2005
    01-Jan-2005 01:45:00    5.37    01-Jan-2005
    01-Jan-2005 02:00:00    5.36    01-Jan-2005
    01-Jan-2005 02:15:00    5.27    01-Jan-2005
    01-Jan-2005 02:30:00    5.07    01-Jan-2005
    01-Jan-2005 02:45:00    5.01    01-Jan-2005
    01-Jan-2005 03:00:00    4.94    01-Jan-2005
    01-Jan-2005 03:15:00    4.77    01-Jan-2005
    01-Jan-2005 03:30:00    4.69    01-Jan-2005
    01-Jan-2005 03:45:00    4.66    01-Jan-2005

% Find days that in DateList2 that are also in DateList1
ind = ismember(DateList2.date,DateList1.date) ...
    & hour(DateList2.Time) >= 9 ...
    & hour(DateList2.Time) < 11;

DateList2(ind,:)

ans = 3008×2 timetable
            Time            Var1        date    
    ____________________    _____    ___________

    20-Jan-2005 09:00:00     2.73    20-Jan-2005
    20-Jan-2005 09:15:00     2.76    20-Jan-2005
    20-Jan-2005 09:30:00     2.74    20-Jan-2005
    20-Jan-2005 09:45:00     2.72    20-Jan-2005
    20-Jan-2005 10:00:00     2.75    20-Jan-2005
    20-Jan-2005 10:15:00     2.72    20-Jan-2005
    20-Jan-2005 10:30:00     2.67    20-Jan-2005
    20-Jan-2005 10:45:00      2.7    20-Jan-2005
    28-Jan-2005 09:00:00     -0.2    28-Jan-2005
    28-Jan-2005 09:15:00    -0.39    28-Jan-2005
    28-Jan-2005 09:30:00    -0.37    28-Jan-2005
    28-Jan-2005 09:45:00    -0.21    28-Jan-2005
    28-Jan-2005 10:00:00    -0.19    28-Jan-2005
    28-Jan-2005 10:15:00    -0.22    28-Jan-2005
    28-Jan-2005 10:30:00    -0.26    28-Jan-2005
    28-Jan-2005 10:45:00     -0.2    28-Jan-2005

[Ashfaq Ahmed]

Hi @Cris LaPierre, thank you! This is exactly what I wanted.

Can you also tell me how can I average all the sample temperature from 9:00 to 11:00 am? So that I only end up with one temperature from 20 Jan 2005, one temperature from 28 Jan 2005 and so on and so forth...

[Cris LaPierre]

I would use groupsummary with your groupbins set to 'day' and method set to 'mean'.

load DateList1.mat
load DateList2.mat

DateList2.date = dateshift(DateList2.Time, 'start', 'day');
% Find days that in DateList2 that are also in DateList1
ind = ismember(DateList2.date,DateList1.date) ...
    & hour(DateList2.Time) >= 9 ...
    & hour(DateList2.Time) < 11;

T = DateList2(ind,:);

dayAvg = groupsummary(T,"Time",'day','mean','Var1')

dayAvg = 376×3 table
     day_Time      GroupCount    mean_Var1
    ___________    __________    _________

    20-Jan-2005        8          2.7238  
    28-Jan-2005        8          -0.255  
    05-Feb-2005        8          0.8275  
    13-Feb-2005        8            1.84  
    09-Mar-2005        8          1.9125  
    17-Mar-2005        8           2.005  
    10-Apr-2005        8          6.9125  
    18-Apr-2005        8            8.62  
    26-Apr-2005        8           7.905  
    12-May-2005        8          10.325  
    28-May-2005        8          10.974  
    05-Jun-2005        8          14.269  
    15-Jul-2005        8           19.61  
    23-Jul-2005        8          20.246  
    08-Aug-2005        8          21.062  
    16-Aug-2005        8          23.195  

[Ashfaq Ahmed]

Thank you so much. You really know tons of functions!!