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SUBROUTINE PLTLX (X,Y,TITLE,NCHAR,SIZE,THETA,VSTART,DECSIZ,
X TICK,MODE)
C$ (Draw Labelled and Numbered Logarithmic Axis)
C$ This routine provides for the drawing of a logarithmic axis
C$ with optional labelling and numbering. To maintain space
C$ for labelling, one will normally call PLTLX with (X,Y) at
C$ one of the corners of an inner frame about one inch inside
C$ the page frame. If coordinates are in inches on a 8.5 x 11
C$ inch horizontal page, SIZE = 9.0 or 6.5 inches is
C$ appropriate. If PLTGA or PLTGP is used to plot the graph,
C$ the plot subwindow should be reset to a box of the size set
C$ by the axis lengths in order for the scales to correspond
C$ correctly to the plotted data points. All lettering is
C$ done with routine SYMTXB which can simulate a thick pen of
C$ a diameter settable by a call to SYMPD; this can be used to
C$ enhance the letter quality if desired. It also supports
C$ subscripts, superscripts, kerning, and changes of font,
C$ style, and color.
C$
C$ The arguments are:
C$
C$ (X,Y).....Point from which axis originates.
C$
C$ TITLE.....Hollerith label for the axis. This is always
C$ drawn centered along the axis in the direction
C$ away from (X,Y). Very long titles will be drawn
C$ with smaller characters in order to fit on one
C$ line. leading and trailing blanks are
C$ automatically ignored for the purposes of
C$ centering. The special character sequence "$N"
C$ or "$n" (dollar N) in the string represents a
C$ newline, and may be used to request multi-line
C$ text. For example, the string
C$
C$ "title 1$Ntitle 2$ntitle3"
C$
C$ will generate three lines of the form
C$
C$ title 1
C$ title 2
C$ title 3
C$
C$ In the unlikely event that "$N" is actually
C$ needed in the text, it can be obtained by
C$ bracketing either character with case switch
C$ characters. With the default <PLOT79> case
C$ switch characters, this would be $<N> or <$>N.
C$
C$ NCHAR.... .GT. 0 - Number of characters in TITLE(*).
C$ Normal plot symbols will be used.
C$ .LE. 0 - No title to be drawn.
C$
C$ SIZE......Length of the axis in world units.
C$
C$ THETA.....Counterclockwise angle of inclination of axis in
C$ degrees.
C$
C$ VSTART....Starting value of variable along axis. If it is
C$ not an integral power of ten, a partial decade
C$ will be drawn, so that the starting value will
C$ actually be VSTART, rather than the closest
C$ multiple of ten.
C$
C$ DECSIZ....Number of world units/decade.
C$
C$ TICK..... .GT. 0.0 - Length of tick marks
C$ above (counterclockwise from) the
C$ axis.
C$ .EQ. 0.0 - No tick marks to be drawn.
C$ .LT. 0.0 - Length of tick marks below
C$ (clockwise from) the axis.
C$ A usual value will be TICK = 0.015 on the unit
C$ square, but choosing TICK equal to the length of
C$ the perpendicular axes will form a grid.
C$
C$ MODE......Option flags stored in the low-order bits of the
C$ integer value. These are selected by adding one
C$ or more of the following option values, and then
C$ setting the sign of the resulting sum to select
C$ numbering and titling above (+) or below (-) the
C$ axis.
C$
C$ 1 - Number the axis. Even values of MODE
C$ suppress numbering, but still affect the
C$ choice of tick mark spacing.
C$ 2 - Numbering perpendicular (i.e. rotated -90
C$ degrees) to the axis; otherwise it is
C$ parallel to the axis.
C$ 4 - Omit the first number along the axis. This
C$ can be useful to prevent text overlap when
C$ more than one axis is drawn from a point.
C$ 8 - Omit the last number along the axis.
C$
C$ Any value outside the legal range -15..+15 will
C$ raise an error condition. The usual choice for a
C$ numbered left vertical (Y) axis will be MODE =
C$ +3, and for a numbered lower horizontal (X) axis
C$ will be MODE = -1. The usual choice for an
C$ unnumbered right vertical axis will be MODE = +2
C$ or -2, and for an unnumbered upper horizontal
C$ axis will be MODE = 0.
C$
C$ The sizes and positions of number labels, even if
C$ they are not drawn, affect the choice of where
C$ longer tick marks are drawn. In the common case
C$ where the four sides of a graph have axes, but
C$ two are unnumbered, for the unnumbered axes,
C$ simply subtract 1 from the unsigned MODE value
C$ used for the opposite numbered axis.
C$
C$ (18-Feb-1991)