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

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Ashfaq Ahmed am 8 Jun. 2023
Kommentiert: Ashfaq Ahmed am 8 Jun. 2023
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!
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### Akzeptierte Antwort

Cris LaPierre am 8 Jun. 2023
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.
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Cris LaPierre am 8 Jun. 2023
I would use groupsummary with your groupbins set to 'day' and method set to 'mean'.
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 am 8 Jun. 2023
Thank you so much. You really know tons of functions!!

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