user manual

154
Chapter 8
Function
Result
Description
@OFFSET(FIELD, EXPR, INT)
Any
Performs the s
ame operat i on as the @OFFSET function
with t he addition of a third argument, INT, which
specifies the maximum number of values to look
back. In cases
where the offset is computed from
an expression, this third argument should improve
performance.
For example,
in an expression such as@OFFSET(Foo,
Month, 12), the system knows to keep only the last
twelve values of Foo; otherwise, it has to store
every value j
ust in case. In cases where the offset
value is a constant—including neg at i ve “lookahead”
offsets, which must be constant—the third argument
is pointles
s and the two -argument version of this
function should be used. See also the note about
self-referential funct i ons in the two-a rgument version
described e
arlier.
@SDEV(FIELD)
Real
Returns the standard deviation of values for the
specified FIELD or FIELDS.
@SDEV(FIELD, EXPR)
Real
Returns the standard deviation of values for FIELD
over the last EXPR records received by the curr ent
node, including the current record. FIELD must
be the name of a numeric field. EXPR may be any
expression evaluating to an integ er greater than 0.
If EXPR is omitted, or if it exceeds the number of
records received so far, the standard d eviation over all
of the records received so far is returned.
@SDEV(FIELD, EXPR, INT)
Real
Returns the standard deviation of values for FIELD
over the last EXPR records received by the curr ent
node, including the current record. FIELD must be t he
name of a numeric field. EXPR may be any expression
evaluating to an integer greater than 0. If EXPR
is omitted, or if it exceeds the number of records
received so far, the standard deviation over all of the
records received so far is returned. INT specifies the
maximum number of values to look back. This is far
more efficient than using just two arguments.
@SINCE(EXPR)
Any
Returns the number of records that hav e passed since
EXPR, an arbitrary CLEM expression, was true.
@SINCE(EXPR, INT)
Any
Adding the second argument, INT, specifies the
maximum number of records to look back. If EXPR
has never been true, INT is @INDEX+1.
@SINC
E0(EXPR)
Any
Considers the current record, while @SINCE does not;
@SINCE0 returns 0 if EXPR is true for the current
record.
@SINCE0(EXPR, INT)
Any
Adding the second argument, INT specifies the
maximum number of records to look back.
@SUM(FIELD)
Number
Returns the sum of values for the specified FIELD
or FIELDS.