Using PLPLOT with Fortran

Introduction

PLplot is a software package for creating scientific plots . It is cross-platform ❤, which means it will work on Windows, Unix, and Linux system. The PLplot software is primarily licensed under the LGPL 🔥. It is written in C language, and it has bindings 🔗 for several other language including Fortran 🖥️ .

The PLplot core library can be used to create

• 💥standard x-y plots
• 🔥semi-log plots
• 🚀log-log plots
• 🌤contour plots
• 🌹3D surface plots
• 🌩mesh plots
• 🦁bar charts
• 🥧pie charts.

You can find more about PLPLOT ➡️🖱

Historical remark

A small history of PLPLOT taken from the official documentation is given below.

PLplot was originally developed by Sze Tan of the University of Auckland in Fortran-77. Many of the underlying concepts used in the PLplot package are based on ideas used in Tim Pearson’s PGPLOT package. Sze Tan writes:

I’m rather amazed how far PLPLOT has travelled given its origins etc. I first used PGPLOT on the Starlink VAX computers while I was a graduate student at the Mullard Radio Astronomy Observatory in Cambridge from 1983-1987. At the beginning of 1986, I was to give a seminar within the department at which I wanted to have a computer graphics demonstration on an IBM PC which was connected to a completely non-standard graphics card. Having about a week to do this and not having any drivers for the card, I started from the back end and designed PLPLOT to be such that one only needed to be able to draw a line or a dot on the screen in order to do arbitrary graphics. The application programmer’s interface was made as similar as possible to PGPLOT so that I could easily port my programs from the VAX to the PC. The kernel of PLPLOT was modelled on PGPLOT but the code is not derived from it.

The C version of PLplot was originally developed by Tony Richardson on a Commodore Amiga. That version has been improved and expanded ever since first by Geoffrey Furnish and Maurice Lebrun in the 1990’s and later (after the project was registered at SourceForge on 2000-02-23) with a much-expanded development team.

Installation of binary packages

Ubuntu 🍻

sudo apt-get install libplplot-dev libplplotfortran0

MacOS 🍎

brew install plplot

Building from source

Download the source code

git clone https://git.code.sf.net/p/plplot/plplot plplot-plplot

I have also installed some extra libraries, which are given below.

• libcairo-dev
• libglu1-mesa-dev
• freeglut3-dev
• mesa-common-dev
• pyqt5
• pyqt5-tools

sudo apt install libcairo-dev libglu1-mesa-dev freeglut3-dev mesa-common-dev
pip3 install pyqt5 pyqt5-tools

Building 🪛

After downloading the source code, run the following command inside of terminal

cd plplot-plplot
git branch $(whoami)
git checkout $(whoami)

We will use -DCMAKE_INSTALL_PREFIX to specify the director wherein PLplot will be installed.

cmake -S ./ -B ./build DCMAKE_INSTALL_PREFIX=~/.easifem/extpkgs  -G "Unix Makefiles"
cmake --build ./build --target all
cmake --build ./build --target install

My Configuration: In my case, I want to install PLplot in ~/.easifem/extpkgs. I have already set an environment variable export EASIFEM_EXTPKGS=~/.easifem/extpkgs, so I will use ${EASIFEM_EXTPKGS}, but you can specify the path explicitly.

• -DCMAKE_INSTALL_PREFIX:PATH=~/.easifem/extpkgs
• -DCMAKE_BUILD_TYPE:STRING=Release, other option is Debug
• -DBUILD_SHARED_LIBS:BOOL=ON, set OFF if shared lib are not desired
• -DBUILD_TEST:BOOL=ON, set OFF you dont want to build the tests
• -DENABLE_fortran:BOOL=ON, set OFF, if you dont want fortran bindings
• -DENABLE_lua:BOOL=ON, set OFF if you do not want Lua language bindings

cmake -S ./ -B ~/temp/easifem-extpkgs/plplot/build -G "Unix Makefiles"  -DCMAKE_INSTALL_PREFIX=${EASIFEM_EXTPKGS} -DCMAKE_BUILD_TYPE:STRING=Release -DBUILD_SHARED_LIBS:BOOL=ON  -DBUILD_TEST:BOOL=ON -DENABLE_fortran:BOOL=ON -DENABLE_lua:BOOL=ON

cmake --build ~/temp/easifem-extpkgs/plplot/build --target all

Now you can go to $EASIFEM_EXTPKGS

├── bin
├── include/plplot
├── lib
├── man
└── share

Contents of /bin 📁 is shown below

/bin
├── plserver
├── pltcl
└── pltek

Contents of /include/plplot 📁

├── csadll.h
├── csa.h
├── disptab.h
├── drivers.h
├── pdf.h
├── plConfig.h
├── pldebug.h
├── plDevs.h
├── pldll.h
├── plevent.h
├── plplot.h
├── plplotP.h
├── plstream.h
├── plstrm.h
├── pltcl.h
├── pltk.h
├── plxwd.h
├── qsastimedll.h
├── qsastime.h
├── qt.h
└── tclMatrix.h

Contents of /lib 📁

├── cmake
├── fortran
├── libcsirocsa.so -> libcsirocsa.so.0
├── libcsirocsa.so.0 -> libcsirocsa.so.0.0.1
├── libcsirocsa.so.0.0.1
├── libplfortrandemolib.a
├── libplplotcxx.so -> libplplotcxx.so.15
├── libplplotcxx.so.15 -> libplplotcxx.so.15.0.0
├── libplplotcxx.so.15.0.0
├── libplplotfortran.so -> libplplotfortran.so.0
├── libplplotfortran.so.0 -> libplplotfortran.so.0.2.0
├── libplplotfortran.so.0.2.0
├── libplplotqt.so -> libplplotqt.so.2
├── libplplotqt.so.2 -> libplplotqt.so.2.0.3
├── libplplotqt.so.2.0.3
├── libplplot.so -> libplplot.so.17
├── libplplot.so.17 -> libplplot.so.17.0.0
├── libplplot.so.17.0.0
├── libplplottcltk_Main.so -> libplplottcltk_Main.so.1
├── libplplottcltk_Main.so.1 -> libplplottcltk_Main.so.1.0.1
├── libplplottcltk_Main.so.1.0.1
├── libplplottcltk.so -> libplplottcltk.so.14
├── libplplottcltk.so.14 -> libplplottcltk.so.14.1.0
├── libplplottcltk.so.14.1.0
├── libqsastime.so -> libqsastime.so.0
├── libqsastime.so.0 -> libqsastime.so.0.0.1
├── libqsastime.so.0.0.1
├── libtclmatrix.so -> libtclmatrix.so.10
├── libtclmatrix.so.10 -> libtclmatrix.so.10.3.0
├── libtclmatrix.so.10.3.0
├── pkgconfig
└── plplot5.15.0
-plplot5.15.0
└── drivers
    ├── mem.driver_info
    ├── mem.so
    ├── ntk.driver_info
    ├── ntk.so
    ├── null.driver_info
    ├── null.so
    ├── ps.driver_info
    ├── ps.so
    ├── qt.driver_info
    ├── qt.so
    ├── svg.driver_info
    ├── svg.so
    ├── tk.driver_info
    ├── tk.so
    ├── tkwin.driver_info
    ├── tkwin.so
    ├── xfig.driver_info
    ├── xfig.so
    ├── xwin.driver_info
    └── xwin.so

The lib/cmake directory 📁 contains files necessary for using PLplot with CMake. The contents of this directory are given below.

├── export_csirocsa.cmake
├── export_csirocsa-release.cmake
├── export_mem.cmake
├── export_mem-release.cmake
├── export_ntk.cmake
├── export_ntk-release.cmake
├── export_null.cmake
├── export_null-release.cmake
├── export_plfortrandemolib.cmake
├── export_plfortrandemolib-release.cmake
├── export_plplot.cmake
├── export_plplotcxx.cmake
├── export_plplotcxx-release.cmake
├── export_plplotfortran.cmake
├── export_plplotfortran-release.cmake
├── export_plplotqt.cmake
├── export_plplotqt-release.cmake
├── export_plplot-release.cmake
├── export_plplottcltk.cmake
├── export_plplottcltk_Main.cmake
├── export_plplottcltk_Main-release.cmake
├── export_plplottcltk-release.cmake
├── export_plserver.cmake
├── export_plserver-release.cmake
├── export_pltcl.cmake
├── export_pltcl-release.cmake
├── export_pltek.cmake
├── export_pltek-release.cmake
├── export_ps.cmake
├── export_ps-release.cmake
├── export_qsastime.cmake
├── export_qsastime-release.cmake
├── export_qt.cmake
├── export_qt-release.cmake
├── export_svg.cmake
├── export_svg-release.cmake
├── export_tclmatrix.cmake
├── export_tclmatrix-release.cmake
├── export_tk.cmake
├── export_tk-release.cmake
├── export_tkwin.cmake
├── export_tkwin-release.cmake
├── export_xfig.cmake
├── export_xfig-release.cmake
├── export_xwin.cmake
├── export_xwin-release.cmake
├── plplotConfig.cmake
├── plplotConfigVersion.cmake
└── plplot_exports.cmake

The lib/pkgconfig directory contains files necessary for finding PLplot using pkgconfig in CMake projects. The contents of this directory are given below.

├── plplot-c++.pc
├── plplot-fortran.pc
├── plplot.pc
├── plplot-qt.pc
├── plplot-tcl_Main.pc
└── plplot-tcl.pc

The lib/fortran/modules/plplot directory contains Fortran module files as shown below.

├── plfortrandemolib.mod
├── plplot_double.mod
├── plplot_graphics.mod
├── plplot.mod
├── plplot_private_exposed.mod
├── plplot_private_utilities.mod
├── plplot_single.mod
└── plplot_types.mod

After a successful build open your .bashrc or .zshrc and add following lines to it

export PKG_CONFIG_PATH="${PKG_CONFIG_PATH}:${EASIFEM_EXTPKGS}/lib/pkgconfig"

Note: You have to replace ${EASIFEM} with the PLplot installation path.

Subsequently, run the following command inside terminal.

source ~/.bashrc #if bash if default SHELL

or

source ~/.zshrc #if ZSH is default

Running examples

Create a directory test 📁

mkdir test
cd test
curl -o PLplot_example_1.F90 https://api.cacher.io/raw/ae828dbdfa2aebf3af0a/403d8f4836d78bddc387/PLplot_example_1.F90
curl -o CMakeLists.txt https://api.cacher.io/raw/3ca8ef3a43180dba7f35/cbb8263d9026e996d6ca/PLplot_CMakeLists.txt
cmake -B ./build -DFILE_NAME:STRING="PLplot_example_1.F90"
cmake --build ./build
./build/test

The content of CMakeLists.txt is given below

CMAKE_MINIMUM_REQUIRED(VERSION 3.20.0 FATAL_ERROR)
SET(PROJECT_NAME "plplot")
PROJECT(${PROJECT_NAME})
ENABLE_LANGUAGE(Fortran C)
SET(TARGET_NAME "test")

SET(PLplot_INCLUDE_DIR "$ENV{EASIFEM_EXTPKGS}/lib/fortran/modules/plplot" )
SET(PLplot_LIBRARY "$ENV{EASIFEM_EXTPKGS}/lib/libplplot.so" )
SET(PLplot_Fortran_LIBRARY "$ENV{EASIFEM_EXTPKGS}/lib/libplplotfortran.so" )
OPTION(FILE_NAME "File name")
ADD_EXECUTABLE(${TARGET_NAME} ${FILE_NAME})

TARGET_LINK_LIBRARIES(
  ${TARGET_NAME}
  ${PLplot_LIBRARY}
  ${PLplot_Fortran_LIBRARY} )

TARGET_INCLUDE_DIRECTORIES( ${TARGET_NAME} PRIVATE ${PLplot_INCLUDE_DIR} )

You should see the following result.

PLplot_example_1

Example 0

PROGRAM main
  USE easifemBase
  IMPLICIT NONE
  INTEGER, PARAMETER :: NSIZE = 101
  REAL( DFP ), DIMENSION(NSIZE) :: x, y
  REAL( DFP ) :: xmin = 0.0, xmax = 1.0, ymin = 0.0, ymax = 100.0
  INTEGER :: ierr
  ! Prepare data to be plotted.
  x = arange(0, NSIZE-1) / REAL(NSIZE-1, DFP)
  y = ymax * x**2
  ! Parse and process command line arguments
  ierr = PLPARSEOPTS( PL_PARSE_FULL )
  IF(ierr .NE. 0) THEN
    CALL Display( "plparseopts error" )
    STOP
  END IF
  !> Initiate the PLPLOT enviroment
  CALL PLINIT
  ! Create a labelled box to hold the plot.
  ! we have specified the box dimension
  CALL PLENV( xmin, xmax, ymin, ymax, 0, 0 )
  CALL PLLAB( "x", "y=100 x#u2#d", "Simple PLplot demo of a 2D line plot" )
  ! Plot the data that was prepared above.
  CALL PLLINE( x, y )
  ! Close PLplot library
  CALL PLEND
END PROGRAM main

PLINIT

This routine should be called before doing anything with PLPLOT. It is the main initialization routine for PLPLOT.

PLEND

Always call plend to close any output plot files and to free up resources.

PLSDEV

The output device can be a terminal, disk file, window system, pipe, or socket. If the output device has not already been specified when plinit is called, the output device will be taken from the value of the PLPLOT_DEV environment variable. If this variable is not set (or is empty), a list of valid output devices is given and the user is prompted for a choice.

The device can be specified BEFORE calling plinit by:

CALL PLSDEV(STRING::devname)

An ASCII character string containing the device name keyword of the required output device. If devname is NULL or if the first character of the string is a ``?’’, the normal (prompted) start up is used.

Following is the list of device name.

  Plotting Options:
      < 1> xwin       X-Window (Xlib)
      < 2> tk         Tcl/TK Window
      < 3> ps         PostScript File (monochrome)
      < 4> psc        PostScript File (color)
      < 5> xfig       Fig file
      < 6> null       Null device
      < 7> ntk        New tk driver
      < 8> tkwin      New tk driver
      < 9> mem        User-supplied memory device
      <10> wxwidgets  wxWidgets Driver
      <11> psttf      PostScript File (monochrome)
      <12> psttfc     PostScript File (color)
      <13> svg        Scalable Vector Graphics (SVG 1.1)
      <14> pdf        Portable Document Format PDF
      <15> bmpqt      Qt Windows bitmap driver
      <16> jpgqt      Qt jpg driver
      <17> pngqt      Qt png driver
      <18> ppmqt      Qt ppm driver
      <19> tiffqt     Qt tiff driver
      <20> svgqt      Qt SVG driver
      <21> qtwidget   Qt Widget
      <22> epsqt      Qt EPS driver
      <23> pdfqt      Qt PDF driver
      <24> extqt      External Qt driver
      <25> memqt      Memory Qt driver
      <26> xcairo     Cairo X Windows Driver
      <27> pdfcairo   Cairo PDF Driver
      <28> pscairo    Cairo PS Driver
      <29> epscairo   Cairo EPS Driver
      <30> svgcairo   Cairo SVG Driver
      <31> pngcairo   Cairo PNG Driver
      <32> memcairo   Cairo Memory Driver
      <33> extcairo   Cairo External Context Driver

I prefer one of the following

CALL PLSDEV("qtwidget")
CALL PLSDEV("xwin")
CALL PLSDEV("wxwidgets")

PLENV

The function plenv is used to define the scales and axes for simple graphs.

PLLAB

The function pllab may be called after plenv to write labels on the x and y axes, and at the top of the graph.

PLPOIN

CALL PLPOIN(REAL::X(:),REAL::Y(:),INT::CODE)

If 0 < code < 32, then Hershey symbols is plotted. If 32 <= code <= 127 the corresponding printable ASCII character is plotted.

PLSTRING

CALL PLSTRING(REAL::X(:),REAL::Y(:),STRING::STRING)

Plot a glyph at the specified points. The glyph is specified with a PLplot user string.

## PLSYM

TO BE ADDED LATER.

## COLORS

• PLCOL0
• PLSCOL0
• PLCOLBG

Following example will print black on white

PROGRAM main
 USE easifemBase
 IMPLICIT NONE
 INTEGER, PARAMETER :: NSIZE = 101
 REAL( DFP ), DIMENSION(NSIZE) :: x, y
 REAL( DFP ) :: xmin = 0.0, xmax = 1.0, ymin = 0.0, ymax = 100.0
 INTEGER :: ierr
 ! Prepare data to be plotted.
 x = arange(0, NSIZE-1) / REAL(NSIZE-1, DFP)
 y = ymax * x**2
 ! Parse and process command line arguments
 ierr = PLPARSEOPTS( PL_PARSE_FULL )
 IF(ierr .NE. 0) THEN
   CALL Display( "plparseopts error" )
   STOP
 END IF
 !> Initiate the PLPLOT enviroment
 CALL PLSDEV("qtwidget")
 CALL PLSCOLBG(255,255,255)
 CALL PLINIT
 CALL PLSCOL0(0, 0,0,0)
 CALL PLCOL0(0)
 ! COLOR
 ! Create a labelled box to hold the plot.
 ! we have specified the box dimension
 CALL PLENV( xmin, xmax, ymin, ymax, 0, 0 )
 CALL PLLAB( "x", "y=100 x#u2#d", "Simple PLplot demo of a 2D line plot" )
 ! Plot the data that was prepared above.
 CALL PLPOIN( x, y, 4 )
 ! Close PLplot library
 CALL PLEND
END PROGRAM main