Using very simple syntax, patchline allows you to visualize lines as patches. This allows you to set any valid properties of the patch object, including 'EdgeAlpha' (to modify the transparency of the lines).
Note that the effectiveness of setting the transparency (edgealpha) may differ on different operating systems. Try different Figure Renderers (particularly openGL) to get the desired behavior.

Also, unix users may experience problems if the renderer is not set to "opengl software". This parameter cannot be set at runtime, but can be set in startup.m.

Patchline is useful if you want to create a transparent line or a transparent plot.