Gnuplot vs ggplot2: Commands or the Grammar of Graphics?

Short answer: choose gnuplot if you think in commands — tell the tool exactly what to draw, in order, and save the script. Choose ggplot2 if you think in layers and data mappings, and your analysis already lives in R. Gnuplot is a standalone program; ggplot2 is a package inside the R ecosystem, built on the grammar of graphics idea of building a chart from layered components.

The same task, both ways

The task: a scatter plot of measurements from a data file, grouped by category, saved for a report.

In gnuplot

Gnuplot reads the file directly and draws what the commands say, in the order you give them. Filtering and grouping are expressed with using and separate plot clauses.

set datafile separator comma
set terminal pngcairo size 900,600
set output 'groups.png'
set xlabel 'Length'
set ylabel 'Width'
set key outside
plot 'samples.csv' using 1:2 with points title 'Group data'

The mental model is imperative: set the stage, then plot. There is very little abstraction between you and the final figure, which makes behaviour easy to predict. You can run these commands in the online terminal to feel the workflow.

In ggplot2

Ggplot2 is part of the tidyverse collection of R packages. Instead of issuing drawing commands, you describe mappings — which variable goes to which axis, which variable controls colour — and add layers such as points, smooth lines and facets. Faceting (splitting one chart into a grid of small panels by category) is a particular strength and takes very little code. The trade-off is that you need R, the tidyverse way of organising data, and a different mental model before the first chart appears.

Side-by-side comparison

Dimension	Gnuplot	Ggplot2
Working model	Standalone program; imperative commands in a script file	R package; declarative layers and aesthetic mappings
Learning curve	Gentle; commands read close to what they do	Steeper start; the grammar pays off on complex grouped charts
Grouped and faceted charts	Done with multiplot and repeated plot clauses	A core strength; facets are built into the model
Output quality	Excellent static output, strong LaTeX terminals	Consistent, polished default styling for reports
Ecosystem	Shell scripts, Makefiles, any language can call it	R statistics ecosystem and tidy data tools
Best fit	File-based plotting, papers, automation	Statistical analysis and reporting inside R

Who should pick which?

Pick gnuplot if your data arrives as files, you are not otherwise using R, or your figures must rebuild automatically — for example with the multiplot layout approach for panel figures.

Pick ggplot2 if you analyse data in R, produce grouped statistical charts often, or want faceting and a consistent house style with little manual styling.