Chapter 4: Plotting Axis Systems and Titles
An axis system defines an area on the page for plotting data. Various axis
systems can be plotted to accommodate different applications. For
two-dimensional graphics, a maximum of two parallel X- and Y-axes can be
drawn. The axis system is scaled to fit the range of data points and can be
labeled with values, names and ticks. Two-dimensional axis systems are
plotted with a call to the routine GRAF.
G R A F
GRAF plots a two-dimensional axis system.
- The call is:
- CALL GRAF (XA, XE, XOR, XSTEP, YA, YE, YOR, YSTEP)
- XA, XE
- are the lower and upper limits of the X-axis.
- XOR, XSTEP
- are the first X-axis label and the step between labels.
- YA, YE
- are the lower and upper limits of the Y-axis.
- YOR, YSTEP
- are the first Y-axis label and the step between
labels.
Additional notes:
- GRAF must be called in level 1 and automatically sets
the level to 2. When plotting more than 1 axis system
on a page, ENDGRF must be called in between each new set
of axes in order to set the level back to 1.
- The position of the lower left corner and the size of
an axis system
can be changed with the routines AXSPOS and AXSLEN.
- The axis scaling is linear by default and can be changed
with AXSSCL. For logarithmic scaling, the corresponding
parameters in GRAF must be exponents of base 10.
- One of several label types can be chosen with the routine
LABELS or user-defined with MYLAB.
Single labels can be suppressed by calling AXENDS.
- The routine NAME defines axis titles.
- The number of ticks between axis labels can be changed
with the routine TICKS.
- SETGRF can be used to remove a piece of or complete axis
from an axis system.
- If the numerical value of the lower limit of an axis is
larger than the upper limit and the label step is negative,
axis scaling will be in descending order.
- The
routine FRAME defines the thickness of a frame plotted
around an axis system. A frame can
also be plotted outside of GRAF with the statement
CALL BOX2D.
E N D G R F
The routine ENDGRF terminates an axis system and sets the level back to 1.
- The call is:
- CALL ENDGRF - level 2, 3
T I T L E
This routine plots a title over an axis system. The title may contain up to
four lines of text designated with TITLIN.
- The call is:
- CALL TITLE - level 2, 3
Additional note:
- All lines are centred by default but can
be left- or right-justified using TITJUS.
G R I D
The routine GRID overlays a grid on an axis system.
- The call is:
- CALL GRID (IXGRID, IYGRID) - level 2, 3
- IXGRID, IYGRID
- are the numbers of grid lines between labels.
G R D P O L
The routine GRDPOL plots a polar grid.
- The call is:
- CALL GRDPOL (IXGRID, IYGRID) - level 2, 3
- IXGRID
- is the numbers of circles between labels.
- IYGRID
- is the numbers of sector lines between 360 degrees.
A X G I T
The routine AXGIT plots vertical and horizontal lines through X = 0 and Y = 0.
- The call is:
- CALL AXGIT - level 2, 3
Additional note:
- The statement CALL XAXGIT plots only the
line Y = 0 while CALL YAXGIT plots only X = 0.
C R O S S
The routine CROSS plots vertical and horizontal lines with additional
ticks through X = 0 and Y = 0.
- The call is:
- CALL CROSS - level 2, 3
Additional note:
- The statement CALL XCROSS plots only the
line Y = 0 while CALL YCROSS plots only X = 0.
The following routines plot single X- and Y-axes; they are called secondary
axes because they do not define or change any of the axis scaling parameters.
Secondary axes can be used to add additional labels to the axis systems.
The plotting
routines for
secondary axes are:
- XAXIS plots a linear X-axis - level 1, 2, 3
- YAXIS plots a linear Y-axis - level 1, 2, 3
- XAXLG plots a logarithmic X-axis - level 1, 2, 3
- YAXLG plots a logarithmic Y-axis - level 1, 2, 3
- The call is:
- CALL XAXIS (A, B, OR, STEP, NL, CSTR, IT, NX, NY)
- A, B
- are the lower and upper limits of the axis.
- OR, STEP
- are the first label and the step between labels.
- NL
- is the length of the axis in plot coordinates.
- CSTR
- is a character string containing the axis name.
- IT
- indicates how ticks, labels and the axis name are
plotted. If IT = 0, they are plotted in a clockwise
direction. If IT = 1, they are plotted in an
counter-clockwise direction.
- NX, NY
- are the plot coordinates of the axis start point.
The X-axis will be plotted from left to right and the
Y-axis from bottom to top.
- Analog:
- YAXIS, XAXLG, YAXLG
Additional notes:
- Secondary axes can be called from level 1, 2 or 3.
Note again that secondary axes do not change the
scaling of an axis system defined by GRAF. Similarly,
curves cannot be plotted with only secondary axes,
they require a call to GRAF.
- As in GRAF, the parameters of logarithmic axes
must be exponents of base 10.
- User-defined labels may also be plotted on secondary
axes with MYLAB and the argument 'USER' in the
routine LABELS.
The number of ticks can be changed by calling TICKS.
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