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Programming Note 25/2                                      Page 1


                      EASY GRAPH PLOTTING
                      -------------------



                            Rob Cook
                         Computer Centre
                       La Trobe University
                            21-Jun-77


                            CONTENTS
                            --------

1.0  FUNCTION                                                2

2.0  ATOPLT SUBROUTINES AND CALLING SEQUENCES                3

    2.1  Plotting a Single Graph                             3
    2.2  Plotting Up to 14 Sets of Data on the Same Graph    5
    2.3  Changing Plotting Parameters                        7
    2.4  Obtaining Values of Plotting Parameters             7
    2.5  Plotting the Tick Values as Character Strings      10
    2.6  Plotting Logarithms of Data                        12
    2.7  Plotting Least Squares Lines                       13
    2.8  To Plot One Graph and a Least Squares Line         13
    2.9  Plotting the Tick Values as Integers               15
    2.10 Fixing the Tick Value Increment                    16
    2.11 Fixing One Tick Value                              17
    2.12 Fixing the Origin and Windowing                    18
    2.13 Even Simpler Graph Plotting                        19

3.0  USAGE                                                  20

    3.1  Gould Plotter                                      20
    3.2  Tektronix  4012                                    20
    3.3  Internal Details                                   20
    3.4  Error Messages                                     21


APPENDIX A - ATOPLT Variable Parameters                     A-1

APPENDIX B - Centring Symbols                               B-1
Programming Note 25/2                                      Page 2


1.0  FUNCTION

     Two FORTRAN subroutines ONEPLT and ATOPLT allow a programmer
to  plot graphs of one set of data against another using only one
subroutine call.  Either the Gould plotter or the Tektronix  4012
terminal can be used.

     ONEPLT draws one graph, plotting corresponding values from X
and Y arrays and representing each point by a symbol.  The points
may optionally be joined by straight lines.  The graph  is  drawn
in  a  standard  sized  box with a title along the top edge.  The
data will be scaled so that the graph fits neatly into  the  box,
or  the user may specify the scaling.  Tick marks are drawn along
each edge and scale values are written at every second tick along
the  axes.   The axes are titled, and if necessary the title will
include an exponent multiplier for the tick values.

     ATOPLT will super-impose up to 14 graphs on  the  one  plot.
The data points are represented by different symbols which can be
selected by the programmer.  All the points will be scaled  to  a
single  overall  scale  to  fit into the standard box.  Ranges of
data for various graphs  should  therefore  be  compatible.   The
points  of each graph may optionally be joined by straight lines.
The form of the plot is the  same  as  for  ONEPLT,  except  that
ATOPLT adds a notes box to the right of the graph.  The notes box
contains an explanation for each symbol.

     A third subroutine, ATOPRM, allows the programmer to  change
the values of parameters used by ONEPLT and ATOPLT in drawing the
plot, if the  defaults  are  unsuitable.   The  parameters  whose
values  may be changed, and their default values, are detailed in
Appendix A.

     Other routines allow the plotting of the logarithms of  data
values,  plot  text  as  tick  labels instead of numbers and draw
least squares lines.

     A data set is defined, for the purposes of this document, as
a  set  of  ordered  co-ordinate  pairs  (X,Y)  which  will, when
plotted, be identified by the  same  centred  symbol.   Different
sets are represented by different symbols.
Programming Note 25/2                                      Page 3


2.0  ATOPLT SUBROUTINES AND CALLING SEQUENCES

2.1  Plotting a Single Graph



          CALL ONEPLT(X,Y,N,XTTL,NX,YTTL,NY,HTTL,NH)

X         a real array containing the X data.
Y         a real array containing the Y data.
N         the number of elements in X and Y.
XTTL      either a literal or an  array  containing  the  X  axis
          title.
NX        the number of characters in XTTL.  If  NX  is  negative
          the  symbols  plotted  at the data points are joined by
          straight  line  segments.   The  maximum  is  about  50
          characters.
YTTL      either a literal or an  array  containing  the  Y  axis
          title.
NY        the number of characters in YTTL.  If NY is negative no
          symbols  will  be  drawn  and  the  data points will be
          joined by straight lines.   The  maximum  is  about  30
          characters.
HTTL      either a literal  or  an  array  containing  the  graph
          title.
NH        the number of characters in HTTL.  The maximum is about
          50 characters.
Programming Note 25/2                                      Page 4


C       Example 1
C
        REAL A(8), B(8)
        DATA A /3.45, 2.67, 1.32, 4.44, 2.34, 8.00, 9.04,11.23/
        DATA B /2.33, 4.36, 2.84, 1.23, 4.65, 7.01,11.35,15.24/
C
        CALL ONEPLT(A,B,8,'X data',6,'Y data',6,'Example 1',9)
        END






























C       Example 2
C
        REAL X(100), Y(100)
C
        DO 100 I = 1, 100
          X(I) = I / 2.0
          Y(I) = SIN(X(I)) - X(I)
 100    CONTINUE
        CALL ONEPLT(X,Y,100,'X data',-6,'Y data',6,'Example 2',9)
        END
Programming Note 25/2                                      Page 5


2.2  Plotting Up To 14 Sets Of Data On The Same Graph

     The data arrays X and Y contain the values for up to 14 data
sets.   The  data  sets  are distinguished by introducing a third
array, ISYM, of the same  size.   Each  element  of  ISYM  is  an
integer  (1  to  14)  which  indicates  the data set to which the
corresponding elements  of  X  and  Y  belong.   For  example  if
ISYM(3),  ISYM(6),  and  ISYM(14)  contains  the value 3 then the
points (X(3),Y(3)), (X(6),Y(6)),  (X(14),Y(14)),  belong  to  the
same data set.  The value of an element of ISYM also has a unique
correspondence with a symbol (see table of  symbols  in  Appendix
B),  and  that  symbol is used to plot all points in a particular
data set.  For the example above,  points  (X(3),  Y(3)),  (X(6),
Y(6)) and (X(14), Y(14)) will be represented by the symbol in the
table  corresponding  to  integer  3.   This  method  allows  the
programmer  to  fill  X  and  Y  arrays  in  any order he wishes,
provided that he fills the ISYM array in the same order.  If  any
element  of ISYM is negative the data point corresponding to that
element will be joined to the previous data  point  of  the  same
data set by a straight line.

     Each data set can be identified by a title  written  in  the
notes  box.   The  titles  are specified in the rows of the NOTES
array, one title per symbol used.  The titles may each be  up  to
20  characters  long,  drawn in two lines of ten characters each.
The note contained in the elements (1,1), (1,2), (1,3), (1,4), of
the  array  NOTES are associated with the data set represented by
the lowest absolute valued symbol.  (2,1), (2,2), are  associated
with the second lowest valued symbol and so on.

     The argument values are not altered by ATOPLT.

    CALL ATOPLT (X,Y,ISYM,N,XTTL,NX,YTTL,NY,HTTL,NH,NOTES,NN)

X         a real array containing X values for all the data sets.
Y         a real array containing Y values for all the data sets.
ISYM      an integer array containing values in the range -14  to
          -1  and  1 to 14.  Each element specifies the symbol to
          be drawn for the corresponding (X,Y) point.  Any  other
          values  in  the array will cause the corresponding data
          point to be ignored and a warning message typed.
N         the number of elements in X,Y and ISYM.
XTTL      either a literal or an  array  containing  the  X  axis
          title.
NX        the number of characters in XTTL.  The maximum is about
          60 characters.
YTTL      either a literal or an  array  containing  the  Y  axis
          title.
NY        the number of characters in YTTL.  The maximum is about
          30 characters.
HTTL      either a literal  or  an  array  containing  the  graph
          heading.
NH        the number of characters in HTTL.  The maximum is about
          60 characters.
NOTES     an NN by 4 array containing the notes to  be  drawn  in
          the note box.
NN        the number of notes in XNOTES need not be the  same  as
          the number of symbols used, in which case, the first NN
          symbols  will  be  'noted'  and  extra  notes  will  be
          ignored.
Programming Note 25/2                                      Page 6
































C       Example 3
C
        REAL X(200), Y(200)
        INTEGER ISYM(200), NOTES(2,4)
C
        DATA ISYM/100*1,100*-14/
        DATA (NOTES(1,I),I=1,3)/'Y=Sin(X)    and'/
        DATA (NOTES(2,I),I=1,2)/'Y=Cos(X)'/
C
        DO 100 I = 1, 100
          X(I) = I / 10.0
          X(I+100) = X(I)
          Y(I) = SIN(X(I))
          Y(I+100) = COS(X(I))
 100    CONTINUE
        CALL ATOPLT(X,Y,ISYM,200,'X data',6,'Y data',6,
     *       'Example 3',9,NOTES,2)
        END
Programming Note 25/2                                      Page 7


2.3  Changing Plotting Parameters

     There are 45 parameters in ONEPLT and ATOPLT  which  may  be
set by the user to vary the way the graph is plotted.  This gives
the user with special requirements  considerable  flexibility  to
change the size, shape and details of the graph produced.

     The changeable parameters are numbered 1 to 45 (see Appendix
A  for  definitions  and  default  values).   Default  values are
changed by a call to the  routine  ATOPRM  which  identifies  the
parameters  to  be  altered and supplies new values.  A new value
for any parameter remains in effect for all subsequent  calls  of
ATOPLT and ONEPLT.


                      CALL ATOPRM(N,IP,XP)

N         the number of elements in IP and XP (i.e.   the  number
          of parameters to be changed), limit 45.
IP        an  integer  array   containing   the   integer   codes
          corresponding to the parameters to be changed.
XP        a  real  array  containing  the  new  values   of   the
          parameters.   The  new  values must correspond in order
          with the identifying integers in array IP.



2.4  Obtaining The Values Of ATOPLT Parameters

     The current settings of the ATOPLT parameters can be read by
calling  the ATOGET subroutine.  You will need to read the values
if you want to change them by ATOPRM and set them back  to  their
original  values later, or if you are writing programs to work on
different plotters whose parameters may differ.


                      CALL ATOGET(N,IP,XP)

N         number of parameters to be read
IP        an  integer  array  containing   the   integer   values
          corresponding to the parameters to be read
XP        a real array that receives the current  values  of  the
          parameters
Programming Note 25/2                                      Page 8
































EXAMPLE of use of ATOPRM to produce an overall grid  in  a  graph
box.

        DIMENSION IP(4), XP(4)
C
        DATA IP, XP /7, 26, 27, 8, 220.0, 280.0, -2.0, 0.0/
C
        CALL ATOPRM(4,IP,XP)
        CALL ATOPLT(X,Y,ISYM,200,'X data',6,'Y data',6,
     *       'Example 4',9,NOTES,2)
        END

     This will cause the ticks to be made the same  size  as  the
axis (7 corresponds to X axis tick size, 26 corresponds to Y axis
tick size, both set to default axis  length),  and  half  density
lines  to  be drawn, i.e.  a half density grid will be drawn over
the graph.
Programming Note 25/2                                      Page 9


     The above example depends on the  fixed  numbers  220.0  and
280.0  as  the lengths of the Y and X axes, which is true for the
Gould plotter but not for the Tektronix.  The  ATOGET  subroutine
could  be  used  to  find  the  actual sizes of the axes, and the
program would become independent of plotter and any changes  made
to the axis length.


        DIMENSION IP(4), IG(2), XP(4)
C
        DATA IP, XP /7, 26, 27, 8, 220.0, 280.0, -2.0, 0.0/
        DATA IG /4, 3/
C
        CALL ATOGET (2, IG, XP)
C
        CALL ATOPRM (4, IP, XP)
        CALL ATOPLT(X,Y,ISYM,200,'X data',6,'Y data',6,
     *       'Example 4',9,NOTES,2)
        END
Programming Note 25/2                                     Page 10


2.5  Plotting The Tick Values As Character Strings

     For some applications it is useful to be  able  to  write  a
character  string  at  a  tick instead of a number.  For example,
' Jan ' is more meaningful than  '1.0',  if  you  are  specifying
monthly  data.  This can be done by calling the subroutine ATOCHL
before you call ATOPLT or ONEPLT.  In the  call  to  ATOCHL,  you
specify  an  array containing the labels to be used at successive
ticks.  Each label is a maximum of five characters  and  will  be
centred  on the tick.  So that if your label has three characters
you should specify it as, e.g.  ' Jan '.   The  first  string  is
drawn  at  the  origin and the strings are plotted at every other
tick.

     Character labels are meaningless unless you fill the  values
for  the  ticks,  so  the  ATOCHL  call  allows the programmer to
specify the increment and origin value too.  If you provide  less
labels  than there are ticks, ATOPLT will re-use your labels when
it runs out.  So if you provide ' Jan ' through  to  ' Dec '  and
there are 24 positions, the months will appear twice.

     Once ATOCHL has been used to  set  character  labelling,  it
remains  in effect for all subsequent calls to ATOPLT and ONEPLT,
until a  second  call  to  ATOCHL  is  used  to  unset  character
labelling.

              CALL ATOCHL(IXY,NLAB,TLAB,TINC,ORGV)

IXY       1  :  set X-axis character labels
          2  :  set Y-axis character labels
          -1 :  unset X-axis character labels
          -2 :  unset Y-axis character labels
NLAB      integer number of labels provided; limit 24
TLAB      array containing NLAB labels, each occupying 
          one element and given in A5 format.
TINC      increment in value per tick
ORGV      value at axis origin.
Programming Note 25/2                                     Page 11
































        DIMENSION DAYS(7)
C
        DATA DAYS/' Sun  Mon  Tue  Wed  Thu  Fri  Sat '/
C
        CALL ATOCHL(1,7,DAYS,0.5,0.0)
        CALL ONEPLT(A,B,8,'X data',6,'Y data',6,'Example 5',9)
        END
Programming Note 25/2                                     Page 12


2.6  Plotting Logarithms Of Data

     The logarithms of the data can be  plotted  by  calling  the
subroutine ATOLOG before calling ATOPLT or ONEPLT.  ATOLOG merely
asks ATOPLT to use logarithms;   it  does  not  do  any  plotting
itself.   If  during  subsequent  plotting  any of the data to be
plotted are negative a warning message is typed and the point  is
ignored.

     Once ATOLOG has been used  to  set  logarithm  plotting,  it
remains  in  effect for all subsequent calls to ONEPLT or ATOPLT,
until a  second  call  to  ATOLOG  is  used  to  unset  logarithm
plotting.

                    CALL ATOLOG(IXY)

IXY       1  :  set to plot logarithm of X-data
          2  :  set to plot logarithm of Y-data.
          -1 :  unset to plot logarithm of X-data
          -2 :  unset to plot logarithm of Y-data






























        CALL ATOLOG(1)
        CALL ONEPLT(A,B,8,'X data',6,'Y data',6,'Example 6',9)
Programming Note 25/2                                     Page 13


2.7  Plotting Least Squares Lines

     Users plotting results from experiments may find  it  useful
to  add  the linear least squares line that fits the data points.
Two methods are available.   By  calling  the  subroutine  ATOLSQ
before  calling  ATOLPT  or  ONEPLT, the programmer can ask for a
least squares line to be fitted to any or all of his  data  sets.
By  calling  ATOLSP,  he  can ask for a linear least squares line
that passes through a fixed point, for example [0,0].

     After calls to ATOLSQ or ATOLSP, least squares lines will be
added to plots drawn by all subsequent calls to ATOPLT and ONEPLT
until a second call to ATOLSQ or ATOLSP sets the number of  least
squares lines, N, to zero.

                       CALL ATOLSQ(N,IDS)

N         number of least squares lines (use 1 for ONEPLT)
IDS       array containing N data set indicator values (use 1 for
          ONEPLT)


                   CALL ATOLSP(IDS,XPT,YPT,N)

N         number of last squares lines.
IDS       array containing N data set indicator values
XPT,YPT   arrays of co-ordinates of the fixed points



2.8  To Plot One Graph And A Least Squares Line

     The ONEPLS subroutine is identical to ONEPLT except that  it
adds a least squares line to the plot.

           CALL ONEPLS(X,Y,N,XTTL,NX,YTTL,NY,HTTL,NH)
Programming Note 25/2                                     Page 14
































        CALL ATOLSQ(1,1)
        CALL ONEPLT(A,B,8,'X data',6,'Y data',6,'Example 7',9)

or

        CALL ONEPLS(A,B,8,'X data',6,'Y data',6,'Example 7',9)
Programming Note 25/2                                     Page 15


2.9  Plotting The Tick Values As Integers

     Tick values are normally  plotted  as  REALs  to  2  decimal
places.  The programmer can request INTEGER labels by setting the
appropriate parameter using ATOPRM:


                         Parameter      Value

X-axis INTEGER labels        37          1.0
Y-axis INTEGER labels        38          1.0






























        CALL ATOPRM(1,37,1.0)
        CALL ONEPLT(A,B,8,'X data',6,'Y data',6,'Example 8',9)
Programming Note 25/2                                     Page 16


2.10  Fixing The Tick Value Increment

     ATOPLT examines the data to be plotted  and  selects  values
for  the  origin  of each axis and the increment in the value for
each tick, so that axes cover the data  as  closely  as  possible
while still giving 'sensible' numbers at each tick.

     Although the tick numbers are 'sensible'  they  may  not  be
what  the user requires.  One way of getting better results is to
specify the increment in value for each tick by a call to ATOPRM.
To  do  this effectively, you need to have some idea of the range
of your data and to be aware that ATOPLT writes the tick value on
every   other  tick,  starting  at  the  origin.   Therefore  the
        -----
specified increment should be  half  the  difference  in  numbers
drawn at the ticks.  A tick value of 0.0 means 'not specified'.


                              Parameter

X-axis tick value increment       33
Y-axis tick value increment       34






























        CALL ATOPRM(1,33,0.5)
        CALL ONEPLT(A,B,8,'X data',6,'Y data',6,'Example 9',9)
Programming Note 25/2                                     Page 17


2.11  Fixing One Tick Value

     Continuing on the same theme, to get a neat labelling for an
axis  may  require  more  than  just  fixing  the increment.  For
example, fixing the increment at 1.0 may give you labels of 1.13,
2.13,  3.13,...,  whereas  you would prefer 1.00, 2.00,...  To do
this you can both fix the increment and insist that a given value
appears  at one tick along the axis.  In this case, you could say
that 2.0 is to be a tick value.  Two ATOPRM  parameters  must  be
used.  You must declare that you are fixing a tick value and give
the value.


                         Parameter      Value

X-fix-value-flag            31           1.0
X fixed value               35          value
Y-fix-value-flag            32           1.0
Y fixed value               36          value



     ATOPLT uses your fixed value (and  increment  if  specified)
and calculates an origin value and tick spacing so that the whole
of your data will fit on to the graph.





























        DIMENSION IP(2), XP(2)
        DATA IP, XP /31, 35, 1.0, 5.0/
C
        CALL ATOPRM(2,IP,XP)
        CALL ONEPLT(A,B,8,'X data',6,'Y data',6,'Example 10',10)
        END
Programming Note 25/2                                     Page 18


2.12  Fixing The Origin And Windowing

     Another alternative is to specify the value at the origin of
the  axis.   ATOPLT  will  "window"  your data, that is, any data
values that fall below your origin will not be plotted and  lines
joining these points to points on the graph will terminate at the
graph border.  If you specify a value increment as well, you  are
fixing the values at the end-points of the axis, because the axis
contains a fixed number of points (that can  be  calculated  from
the  axis  length and the tick spacing) and data will be windowed
at both ends of the axis.


                         Parameter      Value

X-fix-value-flag            31           2.0
X-origin-value              35          value
Y-fix-value-flag            32           2.0
Y-origin-value              36          value






























        DIMENSION IP(2), XP(2)
        DATA IP, XP /31, 35, 2.0, 3.0/
C
        CALL ATOPRM(2,IP,XP)
        CALL ONEPLT(A,B,8,'X data',6,'Y data',6,'Example 11',10)
        END
Programming Note 25/2                                     Page 19


2.13  Even Simpler Graph Plotting

     These subroutines are extremely simple to use, for  example,
for  students without much knowledge of FORTRAN.  Standard titles
are supplied.  Both SIMPLT and SIMPLS  plot  a  graph  given  the
coordinates of the points.  SIMPLS adds a least squares line.

                       CALL SIMPLT(X,Y,N)
and
                       CALL SIMPLS(X,Y,N)

X         array containing X coodinates of points
Y         array containing Y coordinates of points
N         size of X and Y arrays






























        CALL SIMPLT(A,B,8)
Programming Note 25/2                                     Page 20


3.0  USAGE

3.1  Gould Plotter

     There is a library file, PLPLOT.REL, on  the  PIC: directory
containing  ATOPLT  configured for the Gould plotter.  To load or
execute a program that calls ATOPLT, use a command of the form:

          .EXECUTE program, PIC:PLPLOT/SEARCH
          -

In a batch job, add a $INCLUDE card following $FORTRAN cards  but
before the $DATA or $EXECUTE card:

          $INCLUDE PIC:PLPLOT/SEARCH

     Each time a call to  ATOPLT  is  executed  a  file  will  be
created with a name of the form Q??S1.PLT.  All files named *.PLT
are queued to the plotter at logout but they can  be  plotted  at
any time by using the PLOT command to the monitor.



3.2  Tektronix 4012

     The Tektronix terminal must  be  initialized  correctly  for
graph plotting.  If you have any problems use the SET TTY command
at monitor level:

          .SET TTY NO CRLF FORM WIDTH 80
          -

     There is a second library on the PIC:  directory  containing
ATOPLT configured for the Tektronix terminal.  To load or execute
a program that calls ATOPLT, use a command of the form:

          .EXECUTE program, PIC:TKPLOT/SEARCH
          -




3.3  Internal Details

1.  ATOPLT subroutines require at least  6P  of  memory  and  may
    require up to 13P depending on the features used.

2.  Entry parts to ATOPLT are:

    ATOCHL,   ATOGET,   ATOLOG,   ATOLSQ
    ATOLSP,   ATOPLT,   ATOPRM,   ONEPLS
    ONEPLT,   SIMPLS,   SIMPLT

3.  There are a large number  of  concealed  subroutines  in  the
    ATOPLT  system.   They all have names of the form AP????, and
    users are advised not to  use  similar  names  to  avoid  the
    possibility of conflict.  ATOPLT also uses named COMMON areas
    with names of the form AP????.
Programming Note 25/2                                     Page 21


4.  ATOPLT has been written to be as independent as  possible  of
    the  particular  plotter  hardware  and  software.   Any user
    wishing to convert ATOPLT to work  with  some  other  plotter
    should consult PD36.




3.4  Error Messages

1.  %ATPPOR ATOPRM index p out of range.

    ATOPRM parameters must lie in the range 1<p<45.
                                             - -

2.  %ARPPLV ATOPRM parameter p value v is less than n
    %ATPPXV ATOPRM parameter p value v exceeds n.

    Some parameters have limits which cannot be exceeded.

3.  %ATPAPL Attempt to plot log of v - point ignored

    v is a negative number and  ATOPLT  was  asked  to  plot  its
    logarithm.

4.  %ATPTML Too many text labels supplied.

    The user cannot give more than 24 text labels in  a  call  to
    ATOCHL.

5.  %ATPNOV No origin value supplied with text labels.

    Text labelling must be combined with fixing the tick origin.

6.  %ATPIOR XY-axis indicator out of range n

    The XY indicator must be either 1 for the X axis or 2 for the
    Y axis.

7.  %ATPTMD Too many data sets in ATOLSQ call: n.
    %ATPTMD Too many data sets in ATOLSP call: n.

    Only 14 data sets can be used for least squares line drawing.

8.  %ATPIOR Data point I out of range n.

    The data set indicators in the ISYM  array  must  be  in  the
    range -14 to +14.











                            APPENDIX A

                    ATOPLT VARIABLE PARAMETERS



     The values of the parameters given below  may  be  altered,  by
using  the  ATOPRM  subroutine,  allowing  the  ATOPLT  user greater
flexibility in choosing his graph layout.   The  units  of  all  the
values    given    below    are   'plotter   units'   i.e.    mm   *
magnification-factor unless otherwise stated.

     The physical size of the plot is determined by the  paper  size
for  the  Gould  plotter  and  by  the  size  of  the screen for the
Tektronix.  The default parameters are defined so that  the  drawing
fills  the  physical  plotting  area.   The  lengths  of the various
parameters are in plotter units.  Normally these units are  mm,  but
they  can  be altered by setting magnification factors for each axis
which affects all lines drawn in that direction.


                                   Parameter   Gould  Tektronix
                                   ---------   -----  ---------
                                                         4012
                                                         ----

Overall Parameters
------------------

Physical size of the plot in mm   X     1       400.0     200.0
                                  Y     2       260.0     150.0

Magnification factor - 0.5 is     X    28         1.0       1.0
half size and 2.0 double size     Y    29         1.0       1.0

Coordinates of the graph origin   X     5        50.0      27.0
relative to the plot origin       Y     6        15.0      15.0

Lengths of the axes               X     3       280.0     130.0
                                  Y     4       220.0     120.0

Width of the notes box                  9        55.0      41.0

Coordinates of the Program        X    42         0.0       0.0
ID message                        Y    43         5.0       5.0

Close the plot on exit from            30         1.0       1.0
ATOPLT flag 1.0 = close plot
            0.0 = leave plot open
ATOPLT VARIABLE PARAMETERS                                 Page A-2


Titling
-------

Coordinates of X axis title       X    11         8.0      50.0
                                  Y    12         2.0       1.0

Coordinates of Y axis title       X    13        30.0       6.0
                                  Y    14        40.0      40.0

Clearance of plot title from           18         3.0       3.0
top of graph frame (the plot
title is centred over the frame)


Ticks Along the Axes
--------------------

Spacing between ticks on axis     X    10        10.0      10.0
                                  Y    45        10.0      10.0

Height of ticks on each axis      X     7         2.5       2.5
                                  Y    26         2.5       2.5

Difference between heights of           8         1.5       1.5
alternate ticks (one setting
for both axes)

Line density for ticks                 27         1.0       1.0
(1.0 for full density,
-2.0 for half density 
-4.0 for quarter density etc.)

Clearance of labels from               20         2.0       1.5
graph frame

Clearance of log labels exponent       41         0.75      0.75
power for exponents

Integer labels (rather than       X    37         0.0       0.0
reals) 0.0=reals; 1.0=integers    Y    38         0.0       0.0

Increment in data values between  X    33         0.0       0.0
ticks. 0.0 means ATOPLT will      Y    34         0.0       0.0
scale values to fit ticks

Fix-tick-value flags              X    31         0.0       0.0
0.0 means no fixed values         Y    32         0.0       0.0
1.0 means that (35,36) give
    tick value
2.0 means that (35,36) give any
    origin value

Fixed tick value or origin        X    35         0.0       0.0
                                  Y    36         0.0       0.0
ATOPLT VARIABLE PARAMETERS                                 Page A-3


Note Box Positioning
--------------------

(X,Y) displacement of first       X    22         5.0       2.0
note line from top left           Y    23         8.0       4.0
corner of note box

Spacing between note lines             24         5.0       5.0


Character Sizes
---------------

Symbols used for ploting points        25         2.0       2.0

Axis titles                       X    15         5.0       5.0
                                  Y    16         5.0       5.0

Plot title                             17         5.0       5.0

Tick label                             19         3.0       2.5

Exponents for log labels               39         2.5       2.5

Exponent powers for log labels         40         2.0       2.0

Program ID                             44         3.0       2.0

Notes                                  21         3.0       3.0











                            APPENDIX B

                          CENTRING SYMBOLS



     Listed below are the symbols plotted at  the  data  points  for
data sets numbered from 1 to 14.