# 3 months average of historical sales the year before

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Hi,

I need to calculate the three months average based on the historical sales data the year before.

For ex: Jan 20 Feb 20 Mar 20 - Average values should go under Jan 21.

100,0,100 - 66.7 Jan 21 value

Please could you suggest the optimal solution for the same? I have attached the screenshots for reference

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I got the logic. 12-9 = 3 which gives the average for 3 months including the current period(Jan 21 value - Jan 21, Jan20, Feb20,)

Thank you so much, Chris

Regards,

Riyaz Pasha

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Try using MOVINGSUM setting the start period as -12, end period -9 and AVERAGE keyword.

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I think the end period instead of -9 should be -10 then values would be right I guess. The test forecast is the line item that has an end period as -9 and the test line item has -10 as end period

Also if you could help me understand the behaviour of the end period.

Thank you

Regards,

Riyaz Pasha

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The start and end dates refer to the relative difference from the time period from which to calculate the aggregation.

-12 would be 12 time periods offset and -9 9 time periods.

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this is difficult for me

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So the value for Jan 21 would include Jan20, Feb20 and Mar20.