Problems with working out averages with large amounts of data

I have a problem with working out averages that hopefully someone one here
can help with.

Please bear with me as i try to explain. Here goes: I currently have a
worksheet that contains two columns, column A has the date and time for data entries over a year. In each day there are a varying amount of data entries. Column B is the data entry for each given time.

for example

A1 = Date/Time B1 = data
A2 = 24/01/2007 17:15 B2 = 1.5
A3 = 24/01/2007 18:00 B3 = 1.2
A26 = 28/01/2007 19:00 B26 =1.8
A245 =04/06/2007 09:15 B245 = 0.6
and so on....

Now the problem is, i need to work out a daily average for each day of data i have but i have over a full years worth of data in this format and each day has varying amounts of data entries ranging from 10 entries to over 30. The way i started to address this problem was to set up an average function of all the results for each day but as i have found out the function cannot be copied as each day has a different amount of readings and therefore the data series for each function changes per day. Doing it this way means creating 365+ functions and then going through each forumla to check that the data series covers the correct data entries. Due to the fact i have over 39000 individual data entries this takes hours and i hope there is someone out there who can suggest a quicker way of doing this?

is there any way i can set up a function to isolate entries per day and then
average them?

many thanks in advance to anyone who can help

Mindblank

Hello Mindblank:

This will sum all the data in column B that are equal to the month number in cell C2 and the day number in cell D2.

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This will count all the days in column A that are equal to the month number in cell C2 and the day number in cell D2.

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thanks very much for your help guys, got it working now, saved many many hours of laborius work.

thanks again

Mindblank