This is a list of requested improvements that I am considering for
possible implementation in future versions of PGPLOT. No promises
are implied! If you have other suggestions, or want me to give high
priority to any of the suggestions, please let me know.
- A double precision version of the library
- Maintaining two parallel versions of the library is
time-consuming, and I do not wish to do so unless there is a clear
need. None of the graphical operations in PGPLOT require double
precision calculations to achieve the accuracy warranted by current
graphics devices, so it is mainly a matter of convenience for
programmers who maintain their data in double precision for other
reasons. Some users have reported success using Fortran compiler
qualifiers to cause REAL variables and constants to be compiled as
double precision; but note that you must also change some of the C
support code and drivers.
- Rotated coordinate systems
- Extend the world-to-device-coordinate transformation to allow
rotation as well as scaling and translation. This would allow
world-coordinate axes that are not parallel to the edge of the
viewport, and would hence cause complications for routines like
PGBOX that label the viewport in world-coordinate space.
- Positioning workstation windows
- Unfortunately there is no way from within a PGPLOT program to
control the location of PGPLOT X-windows. I will consider adding a
new subroutine to the API to specify this, but there are some
potential problems: how should other devices (not X-window)
interpret this? and some X-window managers do not honor position
- Opaque symbols
- An option to make the graph symbols opaque, so that underlying
graphics do not show through (e.g., a circle symbol would consist of a
filled disk in the background color, surrounded by a ring in the
current color, instead of just the ring). There should be solid and
open versions of each symbol.
- User-defined symbols
- A method of defining new symbols that can be used as
graph-markers like the built-in ones.
- Bar and column charts
- An example program is included in PGPLOT v5.2.0 (pgdemo16), and
I intend to include the subroutine in the main pgplot library in a
future version. Comments on the design of this subroutine are
- Surface Plots of 2-D arrays and functions
- To do this properly requires full three-dimensional graphics
capability, which is beyond the scope of PGPLOT. However, a
restricted implementation might be possible. Meanwhile, see demo
- Variable line width
- Allow line width to be a real/float parameter rather than an
integer (this would require new routines: PGSLW and PGQLW would not
- Control of dashed-line appearance
- The ability to set the scaling of the dashed (or dotted or
dash-dotted etc.) line-styles and alter the dash pattern.
- Provide a way to determine whether the active device is true-color
or pseudo-color (with a dynamic lookup table).
- String input
- Put a prompt on a plot and then read back a number or string
with echo, editing, etc. A prototype subroutine to do this is
include in pgdemo14 in version 5.1.0; more work is needed before it
can be included in the PGPLOT library.
- PGPLOT should be able to save the plotting instructions used to
create the current picture so that they can be used to regenerate
the picture on another device (e.g., PostScript copy of the current
X window display). Eileen Berman has implemented something along
these lines by calling the metafile driver in parallel with the
active device driver, but this has some problems that need to be
sorted out before it can be generally implemented.
- Improved cursor input
- Extension of PGCURS/PGBAND to return more information about the
key-stroke, e.g., whether it came from the keyboard or the mouse, and
the state of modifier keys (shift, control, etc.); for devices for
which this is possible. New routine to return cursor position
immediately, without waiting for a keystroke or other event.
- Support for PostScript or other native fonts
- Allow use of arbitrary PostScript fonts on PostScript devices
(and possibly X-window fonts on X-window devices).
- One or more mono-spaced fonts
- Useful for lining things up in columns. (Implementation of
tab-stops in text might help here too.)
- Eight-Bit Character Set
- At present, the PGPLOT routines for displaying text only handle
the 7-bit US-ASCII character set (decimal codes 32-126); some other
characters can be obtained with escape sequences. I propose to
implement all the printable characters of the 8-bit ISO 8859-1
(Latin-1) character set, and possibly provide a way to specify a
different character set. I will also add the `gothic' Hershey fonts
for those who find them appealing. Some people have requested ways
to define their own fonts or add symbols to the font file; I will
look into methods of accommodating this.
- Additional Characters
- e.g., Greek cursive pi (varpi).
- Alternate syntax for text
- A request has been made for an alternate syntax for subscripts,
superscripts, etc.; possibilities include LaTeX/TeX or HTML. This
would only be desirable if it follows an already established
- Ability to change color within a text string
- e.g., with an escape code to specify the color index.
- Improved support for C
- Shared version of libcpgplot; support for PGERRX etc.; better
documentation. Meanwhile, you can make a shared version of
libcpgplot using commands like the following (the ld options are
highly system dependent)
ar -xv libcpgplot.a
ld -o libcpgplot.so -z text -G -i cpg*.o -L . -l pgplot
rm -f cpg*.o
- Improved Contouring Routines
- Routine to label contours with blanking (i.e., a version of
PGCONL for use with PGCONB instead of PGCONT).
- Methods for smoothing data (interpolation to finer grid) before
- Contouring a non-rectangular grid [e.g, with x and y
coordinates of each element supplied by user].
- Better control over labeling in PGCONL, especially orientation
of text (e.g., uphill, downhill, up page, etc.).
- Improved Imaging Routines
- A method to specify an arbitrary transfer function.
- Imaging with non-rectangular pixels (like PGCONX), e.g., for
polar grid; or arbitrary irregular grid [difficult].
- Interpolation between pixels.
- True-color images: Provide a way to specify separate R, G, B
components for each pixel, on devices that permit this, rather than
limiting colors to a 256-entry look-up table.
- A user has requested the option of putting tick marks at
non-integer multiples of the interval, e.g., 0.5 - 2.5 - 4.5 -
- A user has requested logarithmic axes with bases other than
- Log axes that span 1 decade or less not labeled very well.
- A more intelligent version of PGLAB that could figure out where
to put its labels without overlapping with numeric labels on the
axis would be nice.
- More control over the format of numeric labels is needed; e.g., to
specify a fixed number of decimal places.
- A means to suppress labels at either end of an axis when they would
overlap an adjacent plot; e.g,., options in PGBOX.
- Date Axis
- An option in PGAXIS to treat a world-coordinate as a time or date
(e.g., Modified Julian Date) and label the axis with, e.g.:
hours, minutes, seconds
year and day
year, month and day
month and year
day of week.
- A convenient way to produce a legend for a plot: i.e. a list of
symbols, line-styles, etc. with associated text. A general solution
is quite difficult.
- VMS Installation Procedure
- This does not contain a way to extract the documentation from
the source code.
- Circles and Arcs
- Add a circle/arc primitive to the driver interface. Add a PGARC
routine for drawing partial circles (specified by center, radius,
and two angles).
- Window titles
- Add a subroutine to modify the window title on X-window and
similar devices that put a title bar on PGPLOT windows.
- Query routine: number of open devices
- A new routine to return the number of open devices and their
- This routine should indicate to the caller when it has failed
to allocate a view surface of the requested size.
- Cubic splines
- PGPLOT draws curves by linear interpolation between a set of
points (straight-line segments). I plan to add a routine to draw a
smoother curver through the points, e.g., a cubic spline. Smoothing
measured data, i.e., drawing a smooth curve that does not
pass through all the points, is beyond the scope of PGPLOT. The
choice of the best way to smooth the data depends on the
characteristics of the data, and you should smooth the data with an
appropriate method before passing them to PGPLOT.
- Driver for CGM (Computer Graphics Metafile)
- This is an official standard interchange format, but not widely
adopted. David Billinghurst has contributed a driver, layered on CD
from NIST. I am testing this driver, and hope to include it in a
future version of PGPLOT.
- Driver for FIG format
- It would be nice to have an editable graphics format, but
PGPLOT will not be able to easily take advantage of XFIG's
capability, for two reasons: (1) text will appear in the output
file as vectors, not characters, and so will be difficult to edit;
(2) PGPLOT doesn't structure the file into hierarchical `objects',
which would be convenient for editing. Extensions to PGPLOT might
make these features possible.
- GIF driver
- Add option for transparent background.
- GIF/PPM/XWD drivers
- Rewrite in C for improved portability (these drivers all use dynamic memory allocation, which is not possible in standard Fortran-77).
- PostScript driver
- Put bounding-box info at head of file [difficult in
- Method of automatically printing PostScript output, or piping
to another program.
- PostScript and other drivers
- Mechanism (e.g., environment variable) to set paper size to
e.g., A4 instead of US-letter. Ideally this should work with all
- X-Window driver (/XW, /XS)
- Ability to change mapping of mouse-clicks onto A, D, X;
different mapping for modified button-press events (e.g.,
- Copy some colors from the default color map to private color
map when appropriate to ameliorate problems of color map
- Readout of current cursor position. This is not possible to do
except while the cursor is in the current PGPLOT window. This may
be addressed in the Motif driver.
- User-selectable run-time cross-hair cursor (currently can be
selected by changing Xdefaults or under program control). May also
be addressed in Motif driver.
Tim Pearson, California Institute of Technology,
Copyright © 1995-1999 California Institute of Technology