StDevP – PB Docs 126

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

Argument

Description

column

The column for which you want the standard
deviation of the values in the rows. Column can
be the column name or the column number preceded by a pound sign
(#). Column can also be an expression that
includes a reference to the column. The datatype of column must
be numeric.

FOR range (optional)

The data to be included in the standard
deviation. For most presentation styles, values for range are:

  • ALL – (Default)
    The standard deviation for all values in column.

  • GROUP n – The standard
    deviation for values in column in the specified
    group. Specify the keyword GROUP followed by the group number: for
    example, GROUP 1.

  • PAGE – The standard deviation for the values
    in column on a page.

For Crosstabs, specify CROSSTAB for range to
indicate the standard deviation for all values in column in
the crosstab.

For Graph objects specify GRAPH and for OLE objects specify OBJECT
to indicate the standard deviation for values in column in the
range specified for the Rows option.

DISTINCT (optional)

Causes StDevP to consider
only the distinct values in column when determining
the standard deviation. For a value of column,
the first row found with the value is used and other rows that have
the same value are ignored.

expresn (optional)

One or more expressions that you want
to evaluate to determine distinct rows. Expresn can
be the name of a column, a function, or an expression.

Return Values

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.

note.png

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:

This expression returns the standard deviation of
the values in group 1 in the column named salary:

This expression returns the standard deviation of
the values in column 4 on the 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:

This expression for a computed field in a crosstab
returns the standard deviation of the values in the qty_ordered
column in the 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:

See Also


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