X-Gnuplot

Made as a portable version of gnuplot, this is a free and open-source software application that enables you to create graphs from mathematical functions in just a few steps. It's geared toward expert users.

Since there is no installation involved, you can drop the program files in any part of the drive and just click the executable to launch gnuplot. Another possibility is to save it to a USB flash drive to directly run it on any computer with minimum effort. Unlike most installers, it doesn't modify Windows registry settings.

The GUI is user-friendly, made from a large window with a very simple look that doesn't put emphasis on graphical elements, yet it's very easy to navigate.

There are numerous options available in the menu bar when it comes to the plot, expressions, functions, general aspects, axes, charts, styles, and 3D.

Projects can be saved with the PLT format and later opened to pick up from where you left off. You can write mathematical functions just like typing text in a common word processor, evaluate expressions, enter complex numbers, as well as input unary, binary or logical operators.

It's possible to work with elementary functions such as random numbers, absolute values or signs, special functions like error and gamma, or statistical functions: normal and inverse normal.

gnuplot lets you define user functions and variables, set borders and the box width, establish the sampling rate, plot 2D or 3D graphs, show logscale, display chart grids, add arrows and labels, set titles, as well as manage data styles, among others.

We haven't come across any stability problems in our tests, as the app didn't hang, crash or prompt error dialogs. It had minimal impact on computer performance, running on low CPU and RAM.

On the other hand, gnuplot's features are not intuitive, and it takes a while to figure out how it works. Nevertheless, it's filled with rich features for plotting graphs using mathematical functions.