C NAME OF PGRM  LOGARITHMIC AXIS PLOTTER
C AUTHOR        CHARLES E. COHN, ARGONNE NATIONAL LABORATORY
C PURPOSE       TO GENERATE LOGARITHMIC AXES FOR CALCOMP GRAPHS
C CALLING STATEMENT IS
C     CALL LOGAX(X,Y,NC,S,THETA,IMAX,NDEC,H,CHARS)
C X AND Y ARE THE COORDINATES OF THE ORIGIN OF THE AXIS IN INCHES
C S IS THE LENGTH OF THE AXIS IN INCHES
C IMAX IS AN INTEGER GIVING THE POWER OF TEN ASSOCIATED WITH THE FAR END
C      OF THE AXIS.
C NDEC IS AN INTEGER GIVING THE (WHOLE) NUMBER OF DECADES INTO WHICH THE
C      AXIS IS DIVIDED. THIS AND THE ABOVE QUANTITY ARE NORMALLY
C      OBTAINED FROM -SCALOG-.
C H IS THE HEIGHT OF THE CHARACTERS IN THE SCALE MARKINGS AND LEGEND
C THE MAGNITUDE OF NC GIVES THE NUMBER OF CHARACTERS IN THE LEGEND.
C IF NC IS POSITIVE, THE SCALE MARKINGS AND LEGEND
C WILL BE PLACED IN THE COUNTERCLOCKWISE DIRECTION FROM THE AXIS,
C OR IN THE CLOCKWISE DIRECTION FOR NC NEGATIVE. FOR A
C CONVENTIONAL GRAPH, THE X-AXIS HAS THETA=0. AND NC NEGATIVE TO PLACE
C THE MARKINGS BELOW THE GRAPH. THE Y-AXIS HAS THETA=90. AND NC POSITIVE
C TO PLACE THE MARKINGS TO THE LEFT OF THE GRAPH.
C CHARS IS A BYTE ARRAY OR ALPHANUMERIC LITERAL CONTAINING THE LEGEND.
      SUBROUTINE LOGAX(X,Y,ND,S,THETA,IMAX,NDEC,H,CHARS)
      BYTE CHARS(1),LEGEND(3)
      DIMENSION Z(9),DSN(9),DCS(9)
      DATA Z(1),Z(2),Z(3),Z(4),Z(5),Z(6),Z(7),Z(8),Z(9)/.3010299,
     1  .1760913,.1249387,.9691001E-1,.7918125E-1,.6694679E-1,
     2 .5799195E-1,.5115252E-1,.4575749E-1/
      NC=ND
      SGN=1.0
      IF(NC)1,2,2
    1 SGN=-1.0
      NC=-NC
    2 TNC=NC+1
      TH=THETA/57.295779513
      CTH=COS(TH)
      STH=SIN(TH)
      XB=X
      YB=Y
      DS=S/FLOAT(NDEC)
      SDS=STH*DS
      CDS=CTH*DS
      DO 3 J=1,9
      TEMP1=Z(J)
      DSN(J)=TEMP1*SDS
    3 DCS(J)=TEMP1*CDS
      HC=H*CTH
      HS=H*STH
      K=IMAX
      TEMP1=2.*SGN
      XA=X+HS*TEMP1
      YA=Y-HC*TEMP1
      CALL PLOT(XA,YA,3)
      CALL PLTX(16)
      XD=X+SGN*HS
      YD=Y-SGN*HC
      DO   21 I=1,NDEC
      XA=XA+CDS
      YA=YA+SDS
      CALL PLOT(XB,YB,1)
      DO 20 J=1,9
      TEMP1=DCS(J)
      TEMP2=DSN(J)
      XC=XB+TEMP1
      YC =YB+TEMP2
      CALL PLOT(XC,YC,1)
      XD=XD+TEMP1
      YD=YD+TEMP2
      IF(J-9)18,19,19
   18 CALL PLOT(XD,YD,1)
      CALL PLOT(XC,YC,1)
   19 XB=XC
   20 YB=YC
   21 CALL PLOT(XA,YA,1)
      IMIN=IMAX-NDEC
      IF(IMIN+10)60,60,61
   60 EL=2.14285*H
      GO TO 70
   61 IF(IMAX+10)60,60,63
   63 IF(IMAX-100)64,60,60
   64 IF(IMIN-100)65,60,60
   65 IF(IMIN-10)66,67,67
   67 EL=1.71428*H
      GO TO 70
   66 IF(IMAX-10)68,67,67
   68 IF(IMIN)67,69,69
   69 IF(IMAX)67,71,71
   71 EL=1.28571*H
   70 XA=XB-(EL+0.2*H)*SGN*STH-EL
      TEMP1=.5*H
      YA=YB+1.3*SGN*HC-TEMP1
      XC=XA+1.8*H
      YC=YA+TEMP1
      N=NDEC+1
      DO 30 I=1,N
      CALL SETGRF(XA,YA,0.,H,2,2H10)
      IF (K+10) 40,40,41
   40 NP=1
   41 IF(K)42,44,43
   42 NP=2
      GO TO 50
   43 IF(K-10)44,45,45
   44 NP=3
      GO TO 50
   45 IF(K-100)42,40,40
  111 FORMAT(I3)
   50 ENCODE(3,111,LEGEND)K
  114 CALL SETGRF(XC,YC,0.,H,4-NP,LEGEND(NP))
      XA = XA - CDS
      XC = XC  - CDS
      YA = YA  -  SDS
      YC =   YC - SDS
      K=K-1
   30 CONTINUE
      XB =  0.5*S - TNC*H*.42857142
      YB =   (3.5*SGN  - .5)*H
      XA =  X  +XB*CTH-(YB+(EL+0.5*H)*SGN)*STH
      YA = Y +   XB*STH +    YB*CTH
      CALL SETGRF(XA,YA,THETA,H,NC,CHARS)
      RETURN
      END