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VB.NET - Need to get average of data in datatable

Posted on 2014-10-15
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Last Modified: 2014-10-15
Using VB.NET 2013, I have a database table named 'Measurement' that contains columns of temperature, pressure and flow measurements so I have columns named like: TE01, TE02, PE01, PE02, etc. along with a column with a date/time stamp and a column named 'PHASE' . The PHASE can be either 1, 2, or 3 and I need the AVERAGE of the data from each measurement column only for PHASE 3.

qryMeas = "SELECT * FROM MEASUREMENT WHERE PHASE = 3"
daMeas = new oledbDataAdapter(qryMeas, conStr)
dtMeas = new oledbDataTable

daMeas.Fill(dtMeas)

' At this point dtMeas contains all of the data from the MEASUREMENT database table where PHASE = 3

Now what I need to know is how to get the AVERAGE for each of the measurement columns without adding them up and dividing by the row count. I think there should be a simple way to do this I just can't seem to figure it out.

Can someone provide sample code that they know works. I have looked on the Microsoft website regarding Datatable Compute Method but that talks about datasets and objects and I tried adapting their example code but couldn't get it to work.

Help please!

Thanks,
Charlie
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Question by:charlieb01
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4 Comments
 
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Expert Comment

by:Vitor Montalvão
ID: 40381847
Why don't you let the SQL Server do the job?
qryMeas = "SELECT AVG(TE01), AVG(TE02), AVG(PE01), AVG(PE02)
FROM MEASUREMENT 
WHERE PHASE = 3"

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Author Comment

by:charlieb01
ID: 40381860
Vitor,
The problem with the code you suggest is that my code won't always know the names of the columns and there could be as many as 300 columns of sensor readings which would make for a very long query.
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LVL 16

Accepted Solution

by:
Rose Babu earned 500 total points
ID: 40382062
try the below code
Dim avgVal As Integer = -1
Dim strFieldName As String = String.Empty

strFieldName = "TE01" ' You can change it dynamically with the valid column name
avgVal = dtTable.Compute("Avg([" & strFieldName & "])", "")

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Try this and let us know...
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Author Closing Comment

by:charlieb01
ID: 40382669
Perfect, this is exactly what I needed. Tested it and it works perfectly.

Thanks,
Charlie
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