StDevP
DataWindow expression function
Description
Calculates the standard deviation for the specified column. Standard
deviation is a measurement of how widely values vary from average.
Syntax
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StDevP ( column { FOR range { DISTINCT { expres1 {, expres2 {, ... } } } } } ) |
|
Argument |
Description |
|---|---|
|
column |
The column for which you want the standard deviation |
|
FOR range (optional) |
The data to be included in the standard deviation.
For Crosstabs, specify CROSSTAB for For Graph objects specify GRAPH and |
|
DISTINCT (optional) |
Causes StDevP to consider only the distinct values in |
|
expresn (optional) |
One or more expressions that you want to evaluate to |
Return value
Double. Returns the standard deviation for column.
Usage
If you specify range, StDevP returns the standard deviation for
column within range. If you specify DISTINCT, StDevP returns an estimate
of the standard deviation for the distinct values in column, or if you
specify expresn, the estimate of the standard deviation of the rows in
column where the value of expresn is distinct.
For graphs and OLE objects, you do not select the range when you
call the function. The range has already been determined by the Rows
setting on the Data tab page (the Range property), and the aggregation
function uses that range. Settings for Rows include the following:
-
For the Graph or OLE presentation style, Rows is always
All. -
For Graph controls, Rows can be All, Page, or Group.
-
For OLE controls, Rows can be All, Current Row, Page, or Group.
The available choices depend on the layer the control occupies.
Estimating or calculating actual standard
deviation
StDevP assumes that the values in column are the values in all the
rows in the column in the database table. If you did not select all rows
in the column in the SELECT statement, use StDev to compute an estimate of
the standard deviation of a sample.
Not in validation rules or filter
expressions
You cannot use this or other aggregate functions in validation rules
or filter expressions.
Using an aggregate function cancels the effect of setting Retrieve
Rows As Needed in the painter. To do the aggregation, a DataWindow
object always retrieves all rows.
Examples
These examples all assume that the SELECT statement retrieved all
rows in the database table. StDevP is intended to work with a full set of
data, not a subset.
This expression returns the standard deviation of the values in the
column named salary:
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StDevP(salary) |
This expression returns the standard deviation of the values in
group 1 in the column named salary:
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StDevP(salary for group 1) |
This expression returns the standard deviation of the values in
column 4 on the page:
|
1 |
StDevP(#4 for page) |
This expression entered in the Value box on the Data tab page in the
graph’s property sheet returns the standard deviation of the values in the
qty_ordered column in the graph:
|
1 |
StDevP(qty_ordered for graph) |
This expression for a computed field in a crosstab returns the
standard deviation of the values in the qty_ordered column in the
crosstab:
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1 |
StDevP(qty_ordered for crosstab) |
Assuming a DataWindow object displays the order number, amount, and
line items for each order, this computed field returns the standard
deviation of the order amount for the distinct order numbers:
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1 |
StDevP(order_amt for all DISTINCT order_nbr) |
See also