+--------------------------------------------------------------------+
| |
| $THETAI |
| |
+--------------------------------------------------------------------+
MEANING: Gives Instructions for Transforming Initial Thetas
CONTEXT: NM-TRAN Control Record
USAGE:
$THETAI Fortran statements
SAMPLE:
$THI
THETA(1:NTHETA)=LOG(THETAI(1:NTHETA))
THETAP(1:NTHP)=LOG(THETAPI(1:NTHP))
THETA=LOG(THETA)
DISCUSSION:
The purpose of $THETAI is to transform the initial values in the
$THETA and $THETAP records. The record name may also be coded as
$THI.
In the above sample code, it is desired that the thetas by estimated
within NONMEM in the log domain, but the user wants the convenience of
inputting and outputting them in the natural domain, such as when per-
forming linear MU referencing.
The $THETAI record will convert any initial thetas in a $THETA record,
or thetas obtained from a chain file, but will not convert thetas from
an MSF file. The variance to the theta priors will be appropriately
converted when using $PRIOR NWPRI.
The assignment statements may be any Fortran 95 statements. They are
copied unchanged to subroutine SUBROUTINE THETAISUB in FSUBS (also
found in thetair.f90).
They may include array assigment statements specifying the whole
arrays or sections of arrays.
If the initial estimate for an element of theta is transformed, so is |
the upper and lower bounds for that theta, if any.
Arguments of the subroutine are as follows.
THETAI
Values of THETA specified on $THETA records. Input.
THETAPI
Values of THETA specified on $THETAP records (or, if the informa-
tive names are not used, thetas corresponding to priors, if any).
Input.
THETA
New values of THETA. Output.
THETAP
New values of THETA's for priors. Output.
Other reserved variables that may be used are as follows:
NTHETA
Number of thetas to be estimated.
NTHP Number of theta priors.
NPROB IPROB
These can be tested in IF statements so that values may be
assigned diffently for different problems.
If the range is not specified, NONMEM to supply the range (which is by
default NTHETA+NTHP).
When appropriate, for reporting thetas, the inverse function should be
supplied, e.g., with the samples above:
$THR
THETAR(1:NTHETA)=EXP(THETA(1:NTHETA))
THETAPR(1:NTHP)=EXP(THETAP(1:NTHP))
or
THETAR=EXP(THETA)
Note that the assignment occurs after the NONMEM control stream has
been processed, so that errors in assignment of THETA's are not found.
E.g.
$THI
THETA=0.
This will set all theta's to 0, and there will be no specific error
message from NONMEM, though most likely the run will fail.
If initial estimates of all or part of THETA are omitted, NONMEM per-
forms a search for missing initial estimates as its first task.
(These are printed on a separate page under the heading "INITIAL
PARAMETER ESTIMATE"). This search occurs before the transformation by
$THETAI.
Values of INITIAL ESTIMATE OF THETA in NONMEM output are those from
the $THETA/$THETAP records. Values of THETA in the root.ext files are
as set in $THI.
$THI may be used with $THR, but not necessarily.
Another example is rescaling thetas. E.g., suppose in CONTROL5
$THETA (.1,3,5) (.008,.08,.5) (.004,.04,.9)
is replaced with
$THETAI
THETA=THETAI/10.
$THETA (1,30,50) (.08,.8,5) (.04,.4,9)
The results will be identical, except for the values of INITIAL ESTI-
MATE OF THETA in the NONMEM report. The values in .ext will not be
affected.
REFERENCES: Guide Introduction_7
Go to main index.
Created by nmhelp2html v. 1.0 written by Niclas Jonsson (Modified by AJB 5/2006,11/2007,10/2012)