When Ferret starts, several global symbols are set which describe the Ferret version, the date and time when the Ferret session started, and the amount of memory Ferret has allocated. Some of these remain fixed for the Ferret session, and others will be updated later in the Ferret session to reflect the current state of things.
When a plot command is executed, PPLUS automatically defines a number of global symbols which are available to the user with SHOW SYMBOL They are listed here, and also documented in the PPLUS Users Guide. These are not defined until associated plot commands have been issued. Also note that the user cannot redefine the value of these symbols.
Example: draw a plot and examine and use some of the symbols
yes? plot/i=1:10 1./i yes? SHOW SYMBOL ppl$xlen PPL$XLEN = "8.000" ! Try to show an undefined variable (no response) yes? SHOW SYMBOL ppl$lf_var yes? SHOW SYMBOL ppl$line_count PPL$LINE_COUNT = " 1" ! Use the value of a symbol to position a label yes? LET my_xlen = ($ppl$xlen) - 1. DEFINE VARIABLE my_xlen = 8.00 - 1. yes? LABEL/NOUSER `my_xlen`, 0.1, -1, 0, 0.1 "label at `my_xlen`"
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| SYMBOL | PPL COMMAND | DESCRIPTION |
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PPL$EOF |
RD,RWD,SKP |
"YES" if an EOF (end of file) was read. |
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PPL$FORMAT |
FORMAT |
The current format. |
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PPL$HEIGHT |
SIZE |
Height of the box. |
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PPL$INPUT_FILE |
RD,SKP,RWD |
The current input file. |
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PPL$LF_A |
LINFIT |
Constant from fit y= a + b*x |
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PPL$LF_A_STDEV |
LINFIT |
Standard error of A. |
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PPL$LF_B |
LINFIT |
Constant from fit. |
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PPL$LF_B_STDEV |
LINFIT |
Standard error of B. |
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PPL$LF_R2 |
LINFIT |
Regression coefficient squared. |
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PPL$LF_RES_VAR |
LINFIT |
Residual variance. |
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PPL$LF_VAR |
LINFIT |
Total variance. |
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PPL$LINE_COUNT |
- |
The number of the last line read. |
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PPL$PLTNME |
PLTNME |
The name of the plot file. |
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PPL$RANGE_INC |
%RANGE |
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PPL$RANGE_HIGH |
%RANGE |
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PPL$RANGE_LOW |
%RANGE |
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PPL$TEKNME |
TEKNME |
The name of the tektronix file. |
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PPL$VIEW_X |
VPOINT |
X viewpoint (from a WIRE plot) |
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PPL$VIEW_Y |
VPOINT |
Y viewpoint (from a WIRE plot)t |
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PPL$VIEW_Z |
VPOINT |
Z viewpoint (from a WIRE plot) |
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PPL$WIDTH |
SIZE |
Width of the box. |
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PPL$XFACT(n) |
TRANSXY |
Xfact for line n. |
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PPL$XLEN |
AXLEN |
Length of X axis. |
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PPL$XOFF(n) |
TRANSXY |
Xoff for line n. |
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PPL$XORG |
ORIGIN |
Distance between origin and left edge. |
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PPL$XFIRST(n) |
- |
X value for first data point in line n. |
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PPL$XLAST(n) |
- |
X value for last data point in line n. |
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PPL$XMAX |
RD |
Xmax of contour grid |
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PPL$XMIN |
RD |
Xmin of contour grid |
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PPL$XMAX(n) |
- |
Xmax for valid data in line n. |
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PPL$XMIN(n) |
- |
Xmin for valid data in line n. |
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PPL$YFACT(n) |
TRANSXY |
Yfact for line n. |
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PPL$YLEN |
AXLEN |
Length of Y axis. |
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PPL$YOFF(n) |
TRANSXY |
Yoff for line n. |
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PPL$YORG |
ORIGIN |
Distance between origin and bottom edge. |
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PPL$YFIRST(n) |
- |
Y value for first data point in ine n. |
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PPL$YLAST(n) |
- |
Y value for last data point in line n. |
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PPL$YMAX |
RD |
Ymax of contour grid |
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PPL$YMIN |
RD |
Ymin of contour grid |
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PPL$YMAX(n) |
- |
Ymax for valid data in line n. |
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PPL$YMIN(n) |
- |
Ymin for valid data in line n. |
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PPL$ZMAX |
- |
Zmax for valid contour data. |
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PPL$ZMIN |
- |
Zmin for valid contour data. |
In addition to the PPLUS symbols, Ferret sets other symbols on startup or when plotting commands are issued. They are summarized here.
| SYMBOL | FERRET COMMAND | DESCRIPTION |
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FERRET_VERSION |
set at startup |
the Ferret version |
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FERRET_PLATFORM |
set at startup |
the platform Ferret is running on |
| FERRET_MEMORY | set at startup, reset on SET MEMORY/SIZ |
the current memory setting, in Mwords |
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BYTEORDER |
set at startup |
gives "BIG" or "LITTLE" according to the endianness of the CPU |
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set at startup |
date the current Ferret session started |
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SESSION_TIME |
set at startup |
time the current Ferret session started |
| CURRENT_DATE | set when symbol is evaluated | date the symbol is evaluated, e.g. 14-May-09 (available in Ferret v6.2) |
| CURRENT_TIME | set when symbol is evaluated | date the symbol is evaluated, e.g. 15:07:29 (available in Ferret v6.2) |
| DELTA_CPU | initialized at startup, updated when symbol is evaluated | cpu time in seconds used by the Ferret process, since the last time this symbol was evaluated. (available in Ferret v6.2) |
| CLOCK_SECS | initialized at startup, updated when symbol is evaluated | elapsed time in seconds since the Ferret process began. (available in Ferret v6.2) |
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LABTIT |
plot commands |
default title label; if title is set with /TITLE or PPL TITLE, this new title is stored in a movable label |
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LABX |
plot commands |
label for horizontal axis |
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LABY |
plot commands |
label for vertical axis |
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LABn |
plot commands |
nth moveable label |
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LABNUM_X |
plot commands |
label number for X location at upper left, when X axis is normal to the plot |
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LABNUM_Y |
plot commands |
label number for Y location a upper left, when Y axis is normal to the plot |
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LABNUM_Z |
plot commands |
label number for Z location at upper left, when Z axis is normal to the plot |
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LABNUM_T |
plot commands |
label number for T location at upper left, when T axis is normal to the plot |
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LABNUM_DSET |
plot commands |
label number for the dataset label at upper right |
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LABNUM_CALEND |
plot commands |
label number for non-standard calendar time axes, at the upper left |
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LABNUM_YEAR |
plot commands |
label number, year label at upper left, on month or day time series plots |
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LABNUM_DATITL |
plot commands |
label number, dataset title at upper right |
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LABNUM_DODS |
plot commands |
label number, dataset URL at upper right |
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LABNUM_ASPECT |
plot commands |
label number, label for VECTOR/ASPECT at upper left |
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LABNUM_OFFSET |
plot commands |
label number, label for staggered vectors at upper left |
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XAXIS_MIN |
plot commands |
data value corresponding to the start of the horizontal axis |
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XAXIS_MAX |
plot commands |
data value corresponding to the end of the horizontal axis |
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YAXIS_MIN |
plot commands |
data value corresponding to the start of the vertical axis |
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YAXIS_MAX |
plot commands |
data value corresponding to the end of the vertical axis |
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LABKEY |
line PLOT, POLYGON |
text for key of latest line or polygon put on the plot |
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VP_HEIGHT |
SET VIEWPORT |
height of current viewport |
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VP_WIDTH |
SET VIEWPORT |
width of current viewport |
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VP_XLO |
SET VIEWPORT |
lower x corner of viewport, as defined by DEFINE VIEWPORT/XLIM=xlo:xhi |
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VP_XHI |
SET VIEWPORT |
upper x corner of viewport, as defined by DEFINE VIEWPORT/XLIM=xlo:xhi |
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VP_YLO |
SET VIEWPORT |
lower y corner of viewport, as defined by DEFINE VIEWPORT/YLIM=ylo:yhi |
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VP_YHI |
SET VIEWPORT |
upper y corner of viewport, as defined by DEFINE VIEWPORT/YLIM=ylo:yhi |
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VP_RT_MARGIN |
SET VIEWPORT |
width of right margin(see ppl$xorg for left margin) |
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VP_TOP_MARGIN |
SET VIEWPORT |
width of top margin(see ppl$yorg for lower margin) |
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VP_SCALE |
SET VIEWPORT |
shrinking or expansion factor see DEFINE VIEWPORT/TEXT |
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LEV_TEXT |
CONTOUR, SHADE |
command argument used to set levels. |
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LEV_MIN |
CONTOUR, SHADE |
minimum contour level used |
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LEV_MAX |
CONTOUR, SHADE |
maximum contour level used |
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LEV_NUM |
CONTOUR, SHADE |
number of levels used |
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LEV_DEL |
CONTOUR, SHADE |
delta-value between levels |