I have a number of very large datasets of household water consumption which I
want to combine so I have an average reading per house per year (eg I have
four spreadsheets per year, for an area (or subset of area, it is a city, and
some are VERY large)). Each row has an identifier, LotPlan, most of which are
unique, but there are some duplicates (where this is so, they refer to the
same parcel, so I can just average or sum the readings with no problem). I
have deleted all zero records.

What I want to do is run subtotals and average the Avg daily water
consumption per LotPlan (some have four readings, some may only have one).
However, Excel will not let me subtotal, as it gives me the end of data
error, which I figure is related to the size of the spreadsheet. What I was
doing was appending the data so I had one worksheet with all the information,
identified by LotPlan, and also by reading period; however, I cannot do this
either, as then it is more than 65K rows. Are there any ways I can get around
these problems in Excel 2003 or 2007? If not, can I do it in Access or SPSS
or other software? I have 4Gig RAM, although it is still very slow! Thanks
for any help.