There are several software and websites available for drawing transition diagrams or Markov plots freely. Here are a few options:
Graphviz: Graphviz is a popular open-source graph visualization software that can be used to draw transition diagrams. It has a simple syntax for creating graphs and supports various output formats. Graphviz can be downloaded for free from the official website.
draw.io: draw.io is a free online diagramming tool that can be used to create a variety of diagrams, including transition diagrams. It has a user-friendly interface and offers a wide range of shapes, symbols, and templates. The diagrams can be exported in various formats, including PDF, PNG, and SVG.
Lucidchart: Lucidchart is another online diagramming tool that can be used to create transition diagrams. It has a drag-and-drop interface and offers various templates, shapes, and icons. Lucidchart has a free version that allows users to create up to three diagrams.
Microsoft Visio: Microsoft Visio is a powerful diagramming tool that can be used to create complex diagrams, including transition diagrams. It has a wide range of shapes, symbols, and templates, and supports various output formats. However, it is not free and requires a subscription to use.
Omnigraffle: Omnigraffle is a diagramming tool for Mac users that can be used to create transition diagrams. It has a user-friendly interface and offers various templates, shapes, and icons. Omnigraffle is not free and requires a one-time payment to use.