+--------------------------------------------------------------------+
 |                                                                    |
 |                    INFN_INTERPOLATION EXAMPLE 2                    |
 |                                                                    |
 +--------------------------------------------------------------------+

 This  example  is  new  to  NONMEM  7.   It  is an improved version of
 infn1.exa.  In this example, instead of using a stand-alone INFN  sub-
 routine,  $INFN  abbreviated code is used to fill in missing values of
 WT in the THEOPP data set.
 (See control5).

 If WT is recorded on every record, then the $PK block can be  simpler.
 The  $PK  block can be called with every record (no need for CALLFL=1)
 and no special code is needed to save the value of WT  for  subsequent
 records.

 No  "missing  independent variable" data item is needed, so the THEOPP
 data file can be used as-is.  The $ABBR abbreviated code is located in
 file  infnabbr  for convenient re-use.  This is also an example of the
 $ABBR REPLACE feature, which  allows  easy  replacement  of  character
 strings in the included code, and  is also an example of declared sub-
 scripted variables.

 Example fine1 shows how the finedata utility program can  be  used  to
 fill in the values without the use of the INFN routine.

 USAGE:

 $PROB  THEOPHYLLINE   POPULATION DATA
 $INPUT      ID DOSE=AMT TIME CP=DV WT
 $DATA       THEOPP
 $SUBROUTINES  ADVAN2
 $ABBR REPLACE INTVBL=WT
 $ABBR REPLACE NULLVAL=0.0
  INCLUDE 'infnabbr'

 The file infnabbr contains the following:

 ; INFNABBR: ABBREVIATED CODE FOR HELP infn2.exa
 ; THIS INFN BLOCK INTERPOLATES AND EXTRAPOLATES VALUES OF A SINGLE
 ; DATA ITEM CALLED INTVBL.
 ; BY DEFAULT, THE AXIS VARIABLE IS CALLED TIME.
 ; THE CHARACTER STRING NULLVAL DENOTES A NULL VALUE.
 ;
 ; IF THERE IS ONLY ONE NON-NULL VALUE, THIS VALUE IS COPIED TO
 ; ALL NULL VALUES. OTHERWISE:
 ; LINEAR INTERPOLATION IS PERFORMED FOR NULL VALUES THAT
 ; LIE BETWEEN TWO NON-NULL VALUES.
 ; LINEAR EXTRAPOLATION IS PERFORMED FOR VALUES BEFORE THE
 ; FIRST NON-NULL VALUE
 ; LINEAR EXTRAPOLATION IS PERFORMED FOR VALUES AFTER THE
 ; LAST NON-NULL VALUE
 ; INFNABBR CAN BE USED WITH BOTH SINGLE
 ; SUBJECT AND POPULATION DATA SET.
 ; WRITTEN BY AJB 9/2012
 ;
 ; TYPICAL USAGE:
 ; $ABBR REPLACE INTVBL=WT
 ; $ABBR REPLACE NULLVAL=0.0
 ; $ABBR REPLACE TIME=T  (ONLY IF T IS THE AXIS VARIABLE RATHER THAN TIME)
 ;  INCLUDE 'INFNINTERP'
 ;
 ;
 $ABBR DECLARE U(MAXIDS,NO), V(MAXIDS,NO)
 $ABBR DECLARE INTEGER IS
 $ABBR DECLARE INTEGER I, INTEGER J, INTEGER L
 $ABBR DECLARE IVAL(NO)
 $INFN
   ; $INFN FOR COMPUTING INTERPOLATED VALUES OF AN
   ; INDEPENDENT VARIABLE NAMED INTVBL
   ; E.g., INTVBL MIGHT BE WEIGHT
   ; ASSUME THAT INTVBL = NULLVAL  WHEN MISSING.
   ; IS=SUBJECT #
   ; IVAL(IS)= # OF NON-NULL VALUES OF THE INDEP VAR. FOR SUBJECT IS
   ; VI(IS,I) = ITH. NON-NULL VALUE OF THE INDEPENDENT VARIABLE
   ; UI(IS,I) = TIME OF THE ITH. NON-NULL VALUE OF THE INDEPENDENT VARIABLE

    IS=0
    IF (ICALL.EQ.1) THEN
 ; FIRST PASS.  SAVE VALUES OF TIME & INDEP VAR. WHEN INDEP VAR. IS NON-NULL
         DO WHILE (DATA)
         IF (NEWIND < 2) THEN  ; INITIALIZE NEW INDIVIDUAL
           IS=IS+1
           IVAL(IS)=0
         ENDIF
         IF (INTVBL /= NULLVAL) THEN     ; SAVE NON-NULL VALUE
            IVAL(IS)=IVAL(IS)+1
            I=IVAL(IS)
            U(IS,I)=TIME
            V(IS,I)=INTVBL
         ENDIF
       ENDDO
 ; SECOND PASS
         IS=0
         DO WHILE (DATA)
         IF (NEWIND < 2) THEN  ; INITIALIZE NEW INDIVIDUAL
           IS=IS+1
           I=0
         ENDIF
 ; IF INDEP VAR IS MISSING AND WAS ONLY NON-NULL ONCE, COPY IT
         IF (INTVBL == NULLVAL .AND. IVAL(IS) == 1) THEN
             INTVBL=V(IS,1)
         ELSE
          IF (INTVBL /= NULLVAL) THEN  ; COUNT ANOTHER NON-NULL VALUE
             I=I+1
          ELSE  ; CURRENT RECORD HAS NULL VALUE
             IF (I==0) THEN ; EXTRAPOLATE FROM FIRST 2 VALUES
                J=1
                L=2
             ELSEIF (I>0 .AND. I<IVAL(IS)) THEN ; INTERPOL. BEFORE AND AFTER
                J=I
                L=I+1
             ELSEIF (I==IVAL(IS)) THEN  ; EXTRAPOL. FROM LAST 2 VALUES
               J=I-1
               L=I
             ENDIF
             SLOPE=(V(IS,J)-V(IS,L))/(U(IS,J)-U(IS,L))
             INTVBL=V(IS,J)+SLOPE*(TIME-U(IS,J))
          ENDIF
         ENDIF
         ENDDO
    ENDIF

 (See control5).
 (See infn1 example).
 (See fine1 example).

REFERENCES: Guide VI Section VI.A, Figure 37
REFERENCES: Guide  Section Introduction_7

  
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