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Question
Tuesday, March 17, 2009 4:57 PM
Dear,
I have a column: {2,2,null}. If i use datatable.compute to compute the avg of this column, will it return 2 or 1.66? In another word, will this function ignore the null value?
All replies (4)
Tuesday, March 17, 2009 6:02 PM ✅Answered
Ignores, I think you get 2 as the answer.Arjun Paudel
Wednesday, March 25, 2009 5:30 AM ✅Answered | 1 vote
Thanks Martin for the information, Sorry for my answer but I was meaning this way
| Dim dt As New DataTable |
| Dim dc As New DataColumn("Values") |
| dc.DataType = GetType(Double) |
| dt.Columns.Add(dc) |
| Dim dr As DataRow |
| dr = dt.Rows.Add |
| dr(0) = 2 |
| dr = dt.Rows.Add |
| dr(0) = 2 |
| dr = dt.Rows.Add |
| dr(0) = DBNull.Value |
| Dim avg As Double = dt.Compute("avg(Values)", Nothing) |
| MessageBox.Show(avg.ToString) |
| Dim avg1 As Double = dt.Compute("avg(Values)", " Values Is Not Null") |
| MessageBox.Show(avg1.ToString) |
Arjun Paudel
Wednesday, March 25, 2009 4:46 AM | 1 vote
A DataTable has a Compute() method to derive an aggregate value for a column expressed in the following format.
| DataTable.Compute("AggregateFunction(DataColumn)", "condition|Nothing|null") |
The Compute() method is passed two arguments in a comma-separated list of string values. The first argument is the name of an AggregateFunction() which has the name of a DataColumn included within paretheses; this is the DataSet column to which the aggregate function is applied. The second argument restricts the DataRows that are accessed. If all rows of the column are used in the function, there are no restrictions, so a null value (or the keyword Nothing) is passed. Otherwise, a condition is supplied to identify which rows are selected.
Available aggregate functions include those shown in the following table.
| Avg() | The average of values in a column |
| Count() | The number of rows (values) in a column |
| Max() | The largest value in a column |
| Min() | The smallest value in a column |
| StDev() | The standard deviation of values in a column |
| Sum() | The sum of values in a column |
| Var() | The statistical variance of values in a column |
DataTable.Compute method http://msdn.microsoft.com/en-us/library/system.data.datatable.compute.aspx
Related thread: http://forums.asp.net/t/1323498.aspxPlease remember to mark the replies as answers if they help and unmark them if they provide no help.
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Wednesday, March 25, 2009 8:19 AM
Good and neat code sample! You're right.
I test your code sample and it works as you said "Ignores Null value, get 2 as the answer."
Thank you Arjun for your long-time friendly help.
Best regards,
Martin XiePlease remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.