I haven't done much testing of it but would the array formulas:

=MAX((Sheet3!A1:A55000=A1)*Sheet3!C1:C55000)

and:

=LOOKUP(MAX((Sheet1!A1:A55000=A1)*Sheet1!C1:C55000 ),Sheet1!B1:B55000)

work for the maximum reading and time respectively.

Note that if the formulas are in the same sheet as the data then the Sheet1!
is not required.

For the archives enter both formulas with Ctrl + Shift + Enter

--
HTH

Sandy

Replace@mailinator with @tiscali.co.uk


"Ray Wright" wrote in message
...
I have a large dataset (about 55,000 records) that consists of instrument
readings taken at different times on different days (between 24 - 40
readings per day). The data is in the format: Col A - dates; Col B - times
(24 hour clock format); and Col C - instrument readings.



I want to extract (on another worksheet) the maximum instrument reading
per day and the time of that reading (Col A - dates; Col. B - max reading
for the date in Col A; Col. C - time of that reading). I have
successfully extracted the maximum instrument reading with the array
formula:

{=MAX(IF(Sheet1!A1:A55000=A1,Sheet1!C1:C55000))}



However, I have not been able to extract the time of the maximum reading.
Is the solution come combination of INDEX and /or MATCH and/or OFFSET?
Any help appreciated.



I am using XL2002.



Ray Wright