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Moving average microsoft access

Posted on 2010-11-14
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Last Modified: 2012-05-10
I want to calculate a variety of moving averages in microsoft access where I have a table with the columns
Date..Transaction Date in the Microsoft example below
Product descriptuon
Price sold...Currency in the microsoft example below

Microsoft gives an example of a module at the web address below but it only works some of the time and also has problems when i start a new month..all of which suggests I have a problem with my dates which are set at  Date/Time   Fomat Short Date

http://support.microsoft.com/?id=210138  which I have pasted in part below

Option Compare Database

'*************************************************************
'Declarations section of the module.
'*************************************************************

Option Explicit

'===============================================================
' The following function MovAvg computes moving averages based on
' a table with a multiple-field primary key.
'===============================================================


Function MovAvg(currencyType, startDate, period As Integer)
 
    Dim rst As DAO.Recordset
    Dim sql As String
    Dim ma As Currency
    Dim n As Integer
   
    sql = "Select * from table1 "
    sql = sql & "where currencyType = '" & currencyType & "'"
    sql = sql & " and transactiondate <= #" & startDate & "#"
    sql = sql & " order by transactiondate"
   
    Set rst = CurrentDb.OpenRecordset(sql)
    rst.MoveLast
    For n = 0 To period - 1
        If rst.BOF Then
            MovAvg = 0
            Exit Function
        Else
            ma = ma + rst.Fields("rate")
        End If
        rst.MovePrevious
    Next n
    rst.Close
    MovAvg = ma / period

   
     
End Function

I am not skilled in SQL but can understand part of what is written  and create by cut and paste the suggested solution and use it
but as I said it only works part of the time appearing in short period moving averages ( say 5 days) to strike problem as the date
is dropping toward the 12 th of a month the prior 5 days moving average starts to come in error suggesting that as you move from double digit to single digit dates something doesnt work right
I also have problem if my period exceeds about 23 days as I always get a zero on the 1st of the month and sometimes the 2nd

Any help in understanding why I have these problems greatly appreciated
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Question by:snapper1
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Expert Comment

by:Patrick Matthews
Comment Utility
snapper1,

Please restate what you are trying to do, and work up a numerical example.  Posting a sample MDB file would be best of all.

In any event, you probably do NOT need VBA to get a rolling average; a normal SQL statement will probably do the job, and more quickly at that.  Here are two quick examples, using the attached file:

5 day rolling average, by product, for which all days get a rolling average value:


SELECT s1.Product, s1.Date, s1.Quantity, (SELECT Avg(s2.Quantity)
    FROM tblSales s2
    WHERE s2.Product = s1.Product And s2.Date Between DateAdd("d", -4, s1.Date) And s1.Date) AS RollingAvg
FROM tblSales AS s1
ORDER BY s1.Product, s1.Date;

Open in new window



5 day rolling average, by product, for rolling average is null if there are fewer than 5 days:


SELECT s1.Product, s1.Date, s1.Quantity, (SELECT Avg(s2.Quantity)
    FROM tblSales s2
    WHERE s2.Product = s1.Product And s2.Date Between DateAdd("d", -4, s1.Date) And s1.Date
    HAVING Count(s2.Quantity) >= 5) AS RollingAvg
FROM tblSales AS s1
ORDER BY s1.Product, s1.Date;

Open in new window


Cheers,

Patrick
Q-26614461.mdb
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Author Comment

by:snapper1
Comment Utility
Attached is a file I was trying to work off..I am from Australia so my dates 12/11/2010 mean 12th November 2010 etc
Essentially for each date say 12 November ,11/11/2010 etc I am trying to calculate a moving average for the codes in product type using the prices in Rate ie Product type TAH has a price for 12/11/2010 of  7.29 and on 11/11/2010 of 7.36 so a 2 day average would be 7.32 and for 11/11/2010  it would be 7.345 as price on 10/11/2010 is 7.33

I am interested in being able to have several moving averages such as 15, 30 ,60 day being days listed as distinct from calendar days as there is no data for weekend days and would probably use a make table query to output it to another table.

I would like to be able to vary the time of the moving averages

I hope this is a little clearer




 
Database2.accdb
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Expert Comment

by:JVWC
Comment Utility
For Access SQL you will need to convert the dates to US format. eg mmddyyyy
see http://www.mvps.org/access/queries/qry0009.htm

Cheers
JC
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Accepted Solution

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JVWC earned 500 total points
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Author Comment

by:snapper1
Comment Utility
Thanks very much www.adit had the answer on how to convert my au dates to Us dates and then things worked fine

Date

Dates in SQL statements must be in US (United States) short format, and surrounded by the # symbol. For example:

 SQL = “Select * from Employee where StartDate >= #” & _

             Format(StrtDate, “MM/DD/YY”) & “#”

except i used mm/dd/yyyy
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Author Closing Comment

by:snapper1
Comment Utility
defined problem as date issue and gave me a solution with some good articles to rad
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