Add monthly value from one table to daily data in another table by matching month-year

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JAT 2023-1-15

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https://ww2.mathworks.cn/matlabcentral/answers/1894220-add-monthly-value-from-one-table-to-daily-data-in-another-table-by-matching-month-year

评论： Star Strider 2023-1-16

Hi, I have two tables

Table 1 are daily data and Table 2 are monthly data. I am trying to add the monthly value in Table 2 to all the days of that month in Table 1. I have been looking for hours now at examples on this forum using datetime etc to try and match the month and year, but cannot figure it out (I am a newbie). Basically I need to add 4.1193 (from Table 1) to 1-Apr-2013 to 30-Apr-2013 in Table 1, and then 4.8593 (from Table 2) to 1-May-2013 to 31-May-2013 in Table 1 etc. It's a common 'delta change' method so I know there's probably very simple code out there somewhere...

In summary, add Delta_MM for month X year X (Table 2) to all the TAIR values for the days/rows in that same month-year in Table 1. The end result will be a new daily timeseries of 2466 rows.

I had resorted to just going through and copy - pasting it month-by-month (pathetic, I know..), but I need to do this a few times with more data later so I realised I need help...

Can anybody help me please?

Thank you!

Table 1 (2466 x 2) Table 2 (360 x 2)

DateTime TAIR DateTime Delta_MM

01-Apr-2013 -7.5 01-Apr-2013 4.1193

02-Apr-2013 -2.9 01-May-2013 4.8593

03-Apr-2013 0.3 01-June-2013 -0.3856

etc etc etc etc

31-Dec-2019 -1.8 31-Dec-2019 -6.0221

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Answer 1

Star Strider 2023-1-15

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https://ww2.mathworks.cn/matlabcentral/answers/1894220-add-monthly-value-from-one-table-to-daily-data-in-another-table-by-matching-month-year#answer_1148950

I do not have a thorough understanding of what you want to do.

One option could be join, and another could be synchronize.

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JAT 2023-1-15

Hi Star, thanks for the reply and sorry I didn't explain it properly. I had two files, file 1 was a daily timeseries and file 2 was a monthly timeseries. I imported them both into Matlab and now I want to perform an operation where I add the monthly value from file 2 to all the corresponding days of that month in file 1.

Table 1

Table 2 (different size now to what I said in the original question)

So essentially I would like to create 3 new columns in Table 1

Something like the end result being as below, but where I don't have to go through and put the row numbers in the code manually. I thought maybe it could match the month and year in the datetime column to figure it out itself..? It's not a big problem for me to do it manually of course, but I hadn't got this far last night when I posted the question.

AirTemp.minmax26(1:30) = AirTemp.TAIR_ECCC(1:30) + DeltaMid1319.minmax26(1);

AirTemp.minmax45(1:30) = AirTemp.TAIR_ECCC(1:30) + DeltaMid1319.minmax45(1);

AirTemp.minmax85(1:30) = AirTemp.TAIR_ECCC(1:30) + DeltaMid1319.minmax85(1);

AirTemp.minmax26(31:61) = AirTemp.TAIR_ECCC(31:61) + DeltaMid1319.minmax26(2);

AirTemp.minmax45(31:61) = AirTemp.TAIR_ECCC(31:61) + DeltaMid1319.minmax45(2);

AirTemp.minmax85(31:61) = AirTemp.TAIR_ECCC(31:61) + DeltaMid1319.minmax85(2);

AirTemp.minmax26(62:91) = AirTemp.TAIR_ECCC(62:91) + DeltaMid1319.minmax26(3);

AirTemp.minmax45(62:91) = AirTemp.TAIR_ECCC(62:91) + DeltaMid1319.minmax45(3);

AirTemp.minmax85(62:91) = AirTemp.TAIR_ECCC(62:91) + DeltaMid1319.minmax85(3);