___________________________________________________________________
| |
| COPYING BLOCK |
|_________________________________________________________________|
MEANING: Abbreviated code especially for copying pass
CONTEXT: $PRED, $PK, $ERROR, $AES, $DES abbreviated code
SAMPLE:
IF (COMACT.EQ.1) TVCL=CL
DISCUSSION:
Values of variables displayed in tables and scatterplots are obtained
(i.e. copied) from common NMPRD4. There are particular times when
data records are passed to PRED for the purpose of obtaining these
values; these are called copying passes. The variable COMACT signals
that a copying pass is in progress when its value is positive. There
may be a number of copying passes, but if (and only if) values of
variables are to be displayed, there is at least one copying pass.
With the first copying pass, the value of COMACT is 1 and that of MIX-
NUM is 1. If a mixture model with k subpopulations is used, then
COMACT remains 1 during a total of k copying passes, and with each
copying pass the value of MIXNUM increments by 1. If conditional
estimation is used (or if the POSTHOC option appears), then there fol-
lows a set of copying passes where the value of COMACT is 2 and again,
MIXNUM increases from 1 to k. If a mixture model is not used, there
are altogether at most two copying passes, one with COMACT=1 and
another with COMACT=2.
If values of a variable from earlier copying passes are needed in
later passes, the values for the variable should be stored in the SAVE
region of common NMPRD4. (See comsav). When the values are stored in
the SAVE region, that value computed with a given data record during a
copying pass will be found in NMPRD4 when the same record is passed
during the next copying pass, i.e. it will have been saved from the
previous copying pass. This is in contrast to the usual behaviour
(with a noncopying pass), where with a given data record, the value in
NMPRD4 is the value computed with the previous data record. The value
is 0 when a record is passed during the first copying pass, and though
PRED may set it or reset it during a subsequent copying pass, this
need not be done (see discussion below about COMACT).
The values used in tables and scatterplots (whether or not these
values are stored in the SAVE region) are those copied from NMPRD4
with the last copying pass.
A copying block is a block of abbreviated code that is only executed
during a copying pass, i.e. when COMACT has a positive value. Special
rules apply, which allow the user to be less concerned about using the
COMSAV option of the $ABBREVIATED record (see example below):
COM(i) variables that are defined in a copying block are referred to
as explicit SAVE variables. PRED-defined variables that are defined in
a copying block, other than COM(i) variables, are referred to as
implicit SAVE variables. Collectively, the two types of SAVE
variables are referred to as SAVE variables. NM-TRAN stores SAVE
variables in the SAVE region of common NMPRD4.
Implicit and explicit SAVE variables cannot both appear in abbreviated
code. The COMRES option of the $ABBREV record cannot be used when any
implicit SAVE variables are used, but it must be used when explicit
SAVE variables appear (as whenever COM(i) variables appear).
The size of the SAVE region of NMPRD4 depends on the COMSAV option of
the $ABBREV record. This option may be used in three ways:
No COMSAV option. The SAVE region of common NMPRD4 will nonethe-
less include all the SAVE variables.
COMSAV=n (n>=0). NM-TRAN will, if necessary, extend the size of
the SAVE region from n to a larger value so that all SAVE vari-
ables will be included in the region.
COMSAV=-1. There is to be no SAVE region. Variables defined in
a copying block will not be SAVE variables.
EXAMPLE OF USAGE:
$ERROR
Y=F+F*EPS(1)
IPRED=F
IF (COMACT.EQ.1) FT=F
WR=(DV-IPRED)/FT
$EST ... POSTHOC
$TABLE FT IPRED WR
With the first copying pass the value of COMACT is 1, which signals
that during this copying pass, all ETA variables are set to 0. Since
the option POSTHOC appears, with a subsequent copying pass the value
of COMACT is 2, which signals that during this copying pass, all ETA
variables are set to their conditional estimates.
In this example, WR is set to the weighted intra-individual residual.
When COMACT=1, the prediction for the typical individual (ETA=0) is
computed and stored in FT. FT is a SAVE variable, so this value will
have been saved, and when COMACT=2, this same value will be found in
FT. With COMACT=2, the weight used with the residual is computed to
be the reciprocal of this FT value, while IPRED is computed from con-
ditional estimates of the ETA variables and thus its value applies to
to the individual with these estimates, rather than to the typical
individual. The values of IPRED and WR appearing in the table are
those obtained during the last copying pass. The tabled value of
IPRED is based on the conditional estimate of ETA. The value of FT is
also the value obtained during the last copying pass, but it in turn
is also the value obtained from the first copying pass, as the value
of FT has not changed during any subsequent copying pass, and this
value is based on ETA=0.
Since FT is a SAVE variable, a SAVE region will have been allocated
where this variable will be stored, and (unless there is some reason
to use the COMSAV option other than to insure this) the user not be
concerned about this option.
(See comact, nmprd3, nmprd4).
(See abbreviated).
REFERENCES: None.
Go to main index.
Created by nmhelp2html v. 1.0 written by Niclas Jonsson (Modified by AJB 5/2006,11/2007)