.. _uiperturbation:
.. _perturbation:

.. index::
   pair: menu item; Perturbation
   pair: command line option; perturbation
   pair: command; perturbation

Perturbation
============

Perturbation is a simple trick which changes the point at which orbits start.
Traditionally zero is used, but other values can generate interesting results
too.

On enabling this function from the menu, you will be asked for a complex number
specifying the perturbation. It is a toggle; selecting it again resets the
perturbation to zero without prompting.

It can be used to specify a complex number representing a point on the screen.
If you hit the B key instead of using the menu, the current mouse position is
used. This too is a toggle, so B again will disable perturbation by setting it
to zero.

This function only has an effect for certain formulae (like the
:ref:`Mandelbrot set <mandel>`) and only then in :ref:`Mandelbrot mode
<uimandelbrot>`.

**Available as**: menu item

**Syntax**:(perturbation complex)

This is the scripting-language variation of the perturbation function. Instead
of toggling, you always specify the perturbation to use. Use 0 0 to disable
perturbation.

**Available as**: command line option, command