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| EXPECTATION BLOCK |
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MEANING: Abbreviated code for computation of expectations
CONTEXT: Abbreviated code
SAMPLE:
$ERROR
IF (ICALL.EQ.5) THEN
... expectation block ...
ENDIF
DISCUSSION:
An expectation block is a block of abbreviated code that is only exe-
cuted when ICALL=5. This value of ICALL occurs when the marginal
(MRG_) data item is defined in the data set and has a non-zero value
for some records. Expectation blocks are not required when the margi-
nal data item is present, but they allow the user additional func-
tionality. Such blocks may be present in $PRED, $PK, $ERROR.
If the MRG_ data item has the value 1 in a data record, PRED- (PK- and
ERROR-) defined items displayed for the record (e.g. in the row of a
table corresponding to the record) are expectations. When ICALL=5,
the expectations are being computed. With each call to PRED with the
data record, the value being set in Y is contributing to the expecta-
tion being computed for the PRED item, and the value being set for a
PRED-defined item that will be displayed in a table or scatterplot
(except for an item stored in the SAVE region) is contributing to the
expectation being computed for that item.
In this example, the displayed value of PRED with a record having
MRG_=1 is the expectation of the 0-1 variable taking the value 1 if
and only if F > 10.
IF (ICALL.EQ.5) THEN
Y=0
IF (F.GT.10) Y=1
RETURN
ENDIF
Special rules apply to expectation blocks and passes through the data
with ICALL=5.
1) No eta derivatives are computed in an expectation block.
2) Calls to certain NONMEM utility routines are permitted in an
expectation block:
CALL RANDOM(n,R)
where n is an integer 1-10. If CALL RANDOM is present, R
becomes a reserved variable, and may not be used outside the
expectation block. Multiple calls to RANDOM may be present.
3) A RETURN statement may be used in an expectation block. If Y=
appears (i.e. Y is assigned a value) in an expectation block
before the RETURN (not necessarily the in same block containing
the RETURN), then F is set to Y (F=Y); otherwise F is set to to 0
(F=0). If there is no RETURN statement in the expectation block,
then as usual, F is set to the value of Y assigned by the time
PRED (PK, ERROR) exits.
4) Loops are permitted in an expectation block. The syntax is as
follows.
DO WHILE (condition)
.. statements ..
END DO
5) If a mixture model is used, then during calls with ICALL=5, both
MIXNUM and MIXEST are the index of the subpopulation into which
the individual (whose data record is being passed) has been clas-
sified.
(See mrg).
REFERENCES: None.
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