+--------------------------------------------------------------------+
| |
| $ETAS,$PHIS |
| |
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MEANING: Specifies Initial Values for Etas or Phis
CONTEXT: NM-TRAN Control Record
USAGE:
$ETAS [[value1 [value2] [value3] ... [valuen]]
[FILE=filename [FORMAT|DELIM =s] [TBLN=n]]
$PHIS [[value1 [value2] [value3] ... [valuen]]
[FILE=filename [FORMAT|DELIM=s1] [TBLN=n]]
SAMPLE:
$ETAS 0.4 3.0 3.0 5.0
$PHIS 0.4 3.0 3.0 5.0
$ETAS FILE=myprevious.phi FORMAT=s1pE15.8 TBLN=3
$PHIS FILE=myprevious.phi FORMAT=s1pE15.8 TBLN=3
NONMEM describes the use of these records with messages in the report
file such as the following:
LOADED 3 PHI/ETA ITEMS FROM CONTROL STREAM
DISCUSSION:
By default, the initial value used for ETA's in the Estimation Step
search is 0. The $ETAS and $PHIS records provide different initial
estimates. Optional.
OPTIONS:
There are two forms:
$ETAS value1 [value2] [value3] ...[[valuen]
All of the subjects in the data set will be given these initial
values of etas. If fewer values are listed than the number of
etas in the problem, the value 0 will be used for the remaining
etas. Any real value (positive, negative, zero) may be speci-
fied.
When the record is $PHIS, values are entered as phi values, con-
venient for EM methods. The eta values will then be evaluated as
eta(i)=phi(i)-mu(i) for each eta, where mu(i)=mu_i is evaluated
according to their definitions in the $PK section.
FILE=filename FORMAT=s TBLN=n
Uses initial etas and/or phis for an entire set of subjects from
a file .phi or .phm (in the case of mixture problems) of a pre-
vious analysis.
With FORMAT, s defines the delimiter [,|s(pace)|t(ab)] followed
by a Fortran format specification. The default is s1PE12.5. FOR-
MAT should at least have the delimiter appropriate to read the
file. May also be coded DELIM.
For more details, see the format help item:
(See format).
See INTRODUCTION TO NONMEM 7, FORMAT=s1PE11.4
TBLN is the table number in the file. If TBLN is not specified,
it defaults to 1, i.e., the first set of etas/phis are brought
in.
In matching the etas/phis to the data set given in $DATA of the
control stream file, the attempt will be to match ID numbers
rather than subject numbers, if an ID column in the file exists,
which it will, if you are using a .phi or .phm file generated
from a previous nonmem analysis. The phc/etc variances will also
be brought in.
One purpose to bringing initial eta/phi and etc/phc values is you
can readily resume an analysis, if an MSF file was not set up in
the previous analysis (the MSF file system is still the most com-
plete information transfer for resuming an analysis.
FURTHER DISUCSSION
The etas from $ETAS/$PHIS can be used in several ways.
In METHOD=0 (FO), they are ignored, because FO is specifically
designed as a first order Taylor series approximation process centered
around eta=0.
In METHOD=1 (FOCE), they are ignored unless MCETA>0. When MCETA>0,
then various starting etas are tested, including a set from $ETAS,
when available.
In Bayes, SAEM, IMP MAPITER=0 they are used as the starting etas.
In MAP estimation methods, such as METHOD=1, or ITS, or IMP MAPITER>0,
or IMPMAP, and if MCETA>0, then these etas are one of the initial eta
vector positions tested (during the first iteration), and the one giv-
ing the lowest OBJ is then selected.
In cases where FNLETA=2, the estimation step is skipped, and etas
inputted from $ETAS are treated as if they were the final result of an
estimation.
For examples and discussion:
See INTRODUCTION TO NONMEM 7, $ETAS and $PHIS Record For Inputting
Specific Eta or Phi values
REFERENCES: Guide Introduction_7
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Created by nmhelp2html v. 1.0 written by Niclas Jonsson (Modified by AJB 5/2006,11/2007,10/2012)