# Thread: extrapolate a data series (2000 SR1)

1. ## extrapolate a data series (2000 SR1)

I'd like to know how to extrapolate a data series. E.g., given a column of weekly POS sales over the past 52 weeks, what are the projected weekly sales for the next 13 weeks.

2. ## Re: extrapolate a data series (2000 SR1)

This depends on the pattern of the data series. If the sales are seasonal or not, or if other factors affect sales.

If sales are roughly the same week on week, then you can average out the calculation, say (sum([sales])/52) * 13 = that expected for next 13 weeks.

If the pattern of sales varies week on week then you will need to work out what the pattern of sales is.

Easiest way to spot a pattern is to do a graph showing week on week sales.

3. ## Re: extrapolate a data series (2000 SR1)

Thanks! I'll let my customer know.

4. ## Re: extrapolate a data series (2000 SR1)

Bill,

<A target="_blank" HREF=http://www.wopr.com/cgi-bin/w3t/showflat.pl?Cat=&Board=xl&Number=33441&page=&view= &sb=&o=&vc=1>This thread</A> might be interesting for you. It explains how you can use the forecasting tool in Excel, once you've built a model.

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