computer science

PGPLOT

PGPLOT is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand PGPLOT rather than just read about it. In short: PGPLOT is a device-independent graphics subroutine library written starting in 1983 by Tim Pearson, a professor at the California Institute of Technology. PGPLOT is written mostly in FORTRAN with a modular output API that allows output to several dozen types of plotting device.

Key takeaways

PGPLOT belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PGPLOT to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PGPLOT from memory before moving on to harder problems.

Reference excerpt

PGPLOT is a device-independent graphics subroutine library written starting in 1983 by Tim Pearson, a professor at the California Institute of Technology. PGPLOT is written mostly in FORTRAN with a modular output API that allows output to several dozen types of plotting device. PGPLOT has been widely used in the academic and scientific communities, because it provides both low-level (glyph, point, line, and area) plotting primitives and also high-level facilities for drawing graphs. PGPLOT may be redistributed to third parties and modified, but only in binary form. Neither the original nor modified source code are allowed to be redistributed. The most recent version of PGPLOT is 5.2.2, released in February 2001, although third parties have written unofficial patches that include support for additional devices, 64 bit systems, and RGB (true color) plotting. PGPLOT provides C and Fortran 77 interface. There are also several user-contributed bindings, such as C++, perl, python, ruby and tcl/tk. PGPLOT includes device-independent output to many devices including several types of image file, graphics display terminals and plotters, PostScript devices, and X Window. Interactive devices can be used to deliver numeric parameters to the controlling program via a graphics cursor. It is known to run on many operating systems, including most Unix-like systems, MacOS, and Microsoft Windows. In part because of its age, PGPLOT has several limitations compared to newer packages such as PLplot. In particular, PGPLOT supports only 8-bit indexed color graphics, and not full RGB color; and there is no clean way to render graphics directly to an array in program memory. The library PG2PLplot has been developed to aid the transition from PGPlot to PLplot in Fortran programs.

References

External links PGPLOT home page at Caltech

Worked examples

Example 1 — a first encounter with PGPLOT

Start with the simplest possible case. Write down what PGPLOT claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to PGPLOT before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about PGPLOT ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of PGPLOT

In research: PGPLOT appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses PGPLOT in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: PGPLOT is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer graphics stubs, Graphics libraries, so understanding it makes those chapters shorter.
In everyday life: Look for PGPLOT outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study PGPLOT in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PGPLOT means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain PGPLOT out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PGPLOT in simple terms?

Why does PGPLOT matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study PGPLOT?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on PGPLOT.