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Use of VLOOKUP versus more efficient alternative

Posted on 2011-09-14
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All,

I am putting together a Sales and Cost fo Sales forecasting model and am currently using lots (thousands!!) of VLOOKUP to calculate various values.

Tables of data:

Volume - 120+ rows by 68 columns, indexed by Product Code - Dynamic Defined Range "Volume"
Selling Price - same dimensions as Volume, dynamic range "Prices"
Cost of Sales - 24000 rows (all products) by 22 columns, indexed by product code. Defined Range - COS

Tables of calculations, dimensions - 120 Rows x 68 Columns:
Sales - Volume * Selling Price = VLOOKUP(ProdCode,Volume,COLUMN(),False)*VLOOKUP(ProdCode,Prices,COLUMN(),False)
Cost of Sales - Volume * Cost/Kg = VLOOKUP(ProdCode,Volume,COLUMN(),False)*VLOOKUP(ProdCode,COS,n,False)
Cost of Sales is repeated on 3 sheets for Meat, Labour & Packaging

The file is already at 12Mb and is taking a noticeable (20-30secs) time to calculate.

I am using VLOOKUP because its possible that the order of the sheets could change and extra rows could be added so don't want to link the sheets purely on row number.

I need to add the following further calculation tables which will be the same dimensions as the others (120 x 68) and am looking to see if there is a more efficient formula that I can use eg INDEX/MATCH before this becomes an immense beast for our limited laptops (Windows XP, Excel 2003 on Dell Latitude E5400 with 2526Mhz processor and 2Gb of RAM)

Total Cost of Sales - Addition of Meat, Labour & Packaging sheets
Total Margin - Sales less Total Cost of Sales
Summaries of each of the calculation sheets, probably pivot tables.

I realise the Cost of Sales data sheet with 24k rows will be contributing to the file size and doing lookups on this will be contributing to the calculation time. Added complication is that this sheet has the ProdCode as text so having to allow for this in the other sheets.

Any suggestions??? I don't have MS Access so can't transfer it to Access.

I do have Lotus 97 and Approach 97 if that helps but don't have much experience with either. My colleagues that would be looking at it have even less.

Thanks
Rob H
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Question by:Rob Henson
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LVL 11

Expert Comment

ID: 36536492
If the lookup table is sorted on the lookup index, then you can use something like this:

=IF(INDEX(ListOfProdCodes,MATCH(ProdCode,ListOfProdCodes,1))=ProdCode,INDEX(COS,MATCH(ProdCode,ListOfProdCodes,1),ColumnNumberFromCOS),NA())

The trick being that you use the non-exact match function (last argument = 1), which is very fast, and then check whether it does return an exact match.
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LVL 33

Author Comment

ID: 36536520
Would just LOOKUP be more efficient as its not having to look at the whole array?

This would only look at one column and return the value from another column, the layout of all the sheets is the same. In case you were wondering the 68 columns are 18 months worth of weekly forecasting.

Thanks
Rob H
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LVL 11

Accepted Solution

jkpieterse earned 500 total points
ID: 36536625
Hmm, dunno really.
If there are lots of lookups, I'd have just one column using MATCH (using a similar -non-exact-match technique as I show above) to get the proper index from the lookup table and have all subsequent columns use the INDEX function which points to that one MATCH column for its index numbers.
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LVL 33

Author Closing Comment

ID: 36537097
jkpieterse

Combination of INDEX and MATCH works wonderfully!

Each sheet now has a couple of MATCH formulae on each row pulling the row number from the sheets where its needs to get its data from. Each individual calculation now uses an INDEX formula on named ranges for each sheet with the row number from the MATCH formulas.

File size still 13.4Mb but calculation time minimal!

Result!!
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Expert Comment

ID: 36538051
Great!
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