PLplot is a cross-platform software package for creating scientific plots whose (UTF-8) plot symbols and text are limited in practice only by what Unicode-aware system fonts are installed on a user's computer. The PLplot software, which is primarily licensed under the LGPL, has a clean architecture that is organized as a core C library, separate language bindings for that library, and separate device drivers that are dynamically loaded by the core library which control how the plots are presented in noninteractive and interactive plotting contexts.
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 and pie charts. Multiple graphs (of the same or different sizes) may be placed on a single page, and multiple pages are allowed for those device formats that support them.
PLplot has core library support for plot symbols and text specified by the user in the UTF-8 encoding of Unicode. This means for our many Unicode-aware devices that plot symbols and text are only limited by the collection of glyphs normally available via installed system fonts. Furthermore, a large subset of our Unicode-aware devices also support complex text layout (CTL) languages such as Arabic, Hebrew, and Indic and Indic-derived CTL scripts such as Devanagari, Thai, Lao, and Tibetan. Thus, for these PLplot devices essentially any language that is supported by Unicode and installed system fonts can be used to label plots.
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.
We welcome suggestions on how to improve this code, especially in the form of user-contributed enhancements or bug fixes. If PLplot is used in any published papers, please include an acknowledgement or citation of our work, which will help us to continue improving PLplot. Please direct all communication to the plplot-general mailing list.