Calculates an estimate of the variance for the specified column. The variance is the square of the standard deviation.
Var ( column { FOR range { DISTINCT { expres1 {, expres2 {, ... } } } } } )
Argument |
Description |
|---|---|
column |
The column for which you want an estimate for the variance 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 estimate of the variance. For most presentation styles, values for range are:
For Crosstabs, specify CROSSTAB for range:
For Graph and OLE objects, specify one of the following:
|
DISTINCT (optional) |
Causes Var to consider only the distinct values in column when determining the variance. 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. |
Double or decimal if the arguments are decimal. Returns an estimate for the variance for column. If you specify group, Var returns an estimate for the variance for column within group.
If you specify range, Var returns an estimate for the variance for column within range. If you specify DISTINCT, Var returns the variance for the distinct values in column, or if you specify expresn, the estimate for the variance 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 property 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 variance or calculating actual variance
Var assumes that the values in column are
a sample of the values in rows in the column in the database table.
If you select all rows in the column in the SELECT statement,
use VarP to compute the variance of a population.
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.
These examples all assume that the SELECT statement did not retrieve all of the rows in the database table. Var is intended to work with a subset of rows, which is a sample of the full set of data.
This expression returns an estimate for the variance of the values in the column named salary:
Var(salary)
This expression returns an estimate for the variance of the values in the column named salary in group 1:
Var(salary for group 1)
This expression entered in the Value box on the Data property page in the graph’s property sheet returns an estimate for the variance of the values in the quantity column in the graph:
Var(quantity for graph)
This expression for a computed field in a crosstab returns an estimate for the variance of the values in the quantity column in the crosstab:
Var(quantity for crosstab)
Assuming a DataWindow object displays the order number, amount, and line items for each order, this computed field returns the estimate for the variance of the order amount for the distinct order numbers:
Var(order_amt for all DISTINCT order_nbr)
