# AffineTransform¶

class astropy.coordinates.AffineTransform(transform_func, fromsys, tosys, priority=1, register_graph=None)[source]

A coordinate transformation specified as a function that yields a 3 x 3 cartesian transformation matrix and a tuple of displacement vectors.

See Galactocentric for an example.

Parameters: transform_func : callable A callable that has the signature transform_func(fromcoord, toframe) and returns: a (3, 3) matrix that operates on fromcoord in a Cartesian representation, and a CartesianRepresentation with (optionally) an attached velocity CartesianDifferential to represent a translation and offset in velocity to apply after the matrix operation. fromsys : class The coordinate frame class to start from. tosys : class The coordinate frame class to transform into. priority : number The priority if this transform when finding the shortest coordinate transform path - large numbers are lower priorities. register_graph : A graph to register this transformation with on creation, or None to leave it unregistered. TypeError If transform_func is not callable

Methods Summary

 __call__(self, fromcoord, toframe) Does the actual coordinate transformation from the fromsys class to the tosys class.

Methods Documentation

__call__(self, fromcoord, toframe)[source]

Does the actual coordinate transformation from the fromsys class to the tosys class.

Parameters: fromcoord : fromsys object An object of class matching fromsys that is to be transformed. toframe : object An object that has the attributes necessary to fully specify the frame. That is, it must have attributes with names that match the keys of the dictionary that tosys.get_frame_attr_names() returns. Typically this is of class tosys, but it might be some other class as long as it has the appropriate attributes. tocoord : tosys object The new coordinate after the transform has been applied.