PGPLOT Module: PGAXIS -- draw an axis

SUBROUTINE PGAXIS (OPT, X1, Y1, X2, Y2, V1, V2, STEP, NSUB,
: DMAJL, DMAJR, FMIN, DISP, ORIENT)
CHARACTER*(*) OPT
REAL X1, Y1, X2, Y2, V1, V2, STEP, DMAJL, DMAJR, FMIN, DISP
REAL ORIENT
INTEGER NSUB

Draw a labelled graph axis from world-coordinate position (X1,Y1) to
(X2,Y2).

Normally, this routine draws a standard LINEAR axis with equal
subdivisions. The quantity described by the axis runs from V1 to V2;
this may be, but need not be, the same as X or Y.

If the 'L' option is specified, the routine draws a LOGARITHMIC axis.
In this case, the quantity described by the axis runs from 10**V1 to
10**V2. A logarithmic axis always has major, labeled, tick marks
spaced by one or more decades. If the major tick marks are spaced
by one decade (as specified by the STEP argument), then minor
tick marks are placed at 2, 3, .., 9 times each power of 10;
otherwise minor tick marks are spaced by one decade. If the axis
spans less than two decades, numeric labels are placed at 1, 2, and
5 times each power of ten.

If the axis spans less than one decade, or if it spans many decades,
it is preferable to use a linear axis labeled with the logarithm of
the quantity of interest.

Arguments
OPT (input) : a string containing single-letter codes for
various options. The options currently
recognized are:
L : draw a logarithmic axis
N : write numeric labels
1 : force decimal labelling, instead of automatic
choice (see PGNUMB).
2 : force exponential labelling, instead of
automatic.
X1, Y1 (input) : world coordinates of one endpoint of the axis.
X2, Y2 (input) : world coordinates of the other endpoint of the axis.
V1 (input) : axis value at first endpoint.
V2 (input) : axis value at second endpoint.
STEP (input) : major tick marks are drawn at axis value 0.0 plus
or minus integer multiples of STEP. If STEP=0.0,
a value is chosen automatically.
NSUB (input) : minor tick marks are drawn to divide the major
divisions into NSUB equal subdivisions (ignored if
STEP=0.0). If NSUB <= 1, no minor tick marks are
drawn. NSUB is ignored for a logarithmic axis.
DMAJL (input) : length of major tick marks drawn to left of axis
(as seen looking from first endpoint to second), in
units of the character height.
DMAJR (input) : length of major tick marks drawn to right of axis,
in units of the character height.
FMIN (input) : length of minor tick marks, as fraction of major.
DISP (input) : displacement of baseline of tick labels to
right of axis, in units of the character height.
ORIENT (input) : orientation of label text, in degrees; angle between
baseline of text and direction of axis (0-360°).