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 |                    INITIAL ESTIMATE (INITIAL EST)               |
 |_________________________________________________________________|

 MEANING: Initial estimates of parameters THETA, OMEGA, SIGMA
 CONTEXT: NONMEM output

 DISCUSSION:
 Initial estimates of parameters are  required  by  NONMEM.   They  are
 used, for example, to compute the initial value of the objective func-
 tion (before NONMEM begins its search for final estimates).  The  user
 may  provide  initial  estimates.   Alternatively, he may request that
 NONMEM provide initial estimates.

 (NONMEM may also use as initial estimates the final estimates  from  a
 previous    run,   by   means   of   a   Model   Specification   File;
 (See model specification file).  When an MSFI  is  used,  the  outputs
 described here do not appear.)

 NONMEM output reflects initial estimates provided by the user  on  its
 problem summary page as in this example:

      INITIAL ESTIMATE OF THETA:
      LOWER BOUND    INITIAL EST    UPPER BOUND
      0.0000E+00     0.1500E+03     0.1000E+07
      0.0000E+00     0.0000E+00     0.0000E+00
      0.1000E+00     0.3000E+00     0.1000E+02
      -0.1000E+07    -0.1000E-01    0.1000E+07
      INITIAL ESTIMATE OF OMEGA:
      0.2500E+00
      0.0000E+00   0.2500E+00
      INITIAL ESTIMATE OF SIGMA:
      0.2500E+00

      The above states that:

      1)   The initial estimate of theta(1) is 150, and  the  parameter
           is constrained to be greater than zero (no upper bound).

      2)   Theta(1) is fixed at zero.

      3)   The initial estimate of theta(3) is .3, and the parameter is
           constrained to lie between .1 and 10.

      4)   The initial estimate of theta(4) is -.01, and the  parameter
           is unconstrained.

      5)   OMEGA is 2x2 and constrained to be  diagonal  (signified  by
           the  0 value of the initial estimate of omega(2,1); the ini-
           tial estimates of omega(1,1) and omega(2,2) are .25.

      6)   SIGMA is 1x1 (a scalar), with initial estimate .25.

 If the initial estimate of an element of THETA  is  left  blank,  this
 indicates  that the user has requested that NONMEM provide the initial
 estimate, as in this example:

      INITIAL ESTIMATE OF THETA:
      LOWER BOUND    INITIAL EST    UPPER BOUND
      0.1000E+00                    0.1000E+02

 Similarly, if the initial estimate of all  or  part  of  OMEGA  and/or
 SIGMA  is not printed, this indicates that the user has requested that
 NONMEM provide the missing initial estimate(s).

 NONMEM performs a search for missing initial estimates  as  its  first
 task.  The complete set of initial estimates (including those provided
 by the user and those provided by NONMEM) are printed  on  a  separate
 page under the heading "INITIAL PARAMETER ESTIMATE", as in the follow-
 ing example.  The format is identical to that of the "FINAL  PARAMETER
 ESTIMATE"  page.   If  all initial parameter estimates are provided by
 the user, this page does not appear.

       ********************  INITIAL PARAMETER ESTIMATE   ***
       THETA - VECTOR OF FIXED EFFECTS PARAMETERS  **********
                  TH 1      TH 2      TH 3
               1.50E+00  1.02E-01  2.90E+01
       OMEGA - COV MATRIX FOR RANDOM EFFECTS - ETAS  ********
                  ETA1
       ETA1    1.50E+00

 This example is from a run involving single-subject data, so there  is
 no SIGMA matrix.

 (See final parameter estimate).

REFERENCES: Guide IV Section III.B.9, III.B.10, III.B.11


  
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