Radon transform: Circle mode as the default

[josteinbf]

A while ago, we introduced an optional "circle mode". The reasons for this is explained here: #567.

I propose to make this circle mode the default, for the reasons listed in the referenced PR, plus the bonus of consistency with other reconstruction algorithms implemented in skimage. As this is an API change, the code should issue a FutureWarning for at least one release. Since I'm hearing rumours that a new release is approaching, now would be a good time to start issuing the warning.

[ahojnnes]

How about doing the following:

def radon(..., circle=None):
...
if circle is None:
    circle = True
    warn ...

In case circle is not None it must have been set manually by the user?

[josteinbf]

That would be a good way to implement it, yes. But we should probably
discuss whether we want to change the default mode or not before we
implement it?

2013/10/2 Johannes Schönberger notifications@github.com

How about doing the following:

def radon(..., circle=None):
...
if circle is None:
circle = True
warn ...

In case circle is not None it must have been set manually by the user?

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[stefanv]

Is this what most people would want to use? If so, then yes.

[josteinbf]

Everyone doing tomography experiments (myself included) would prefer the
circle=True version, as one simply does not have experimental data for
the part of the image outside the circle. When it comes to studying
tomography reconstruction algorithms, the case is that some algorithms are
more accurate when restricting the reconstruction to a circular region
(applies to SART and other algebraic techniques, but not to the FBP). My
opinion is that the circle mode should be the default as it provides a more
"fair" comparison between algorithms. Although I believe people researching
improved algorithms would agree, I can't be entirely sure here since I do
not actively research improved reconstruction algorithms myself.

In conclusion, I think it is a good idea to change the default. But we
should of course document clearly the difference between the two modes (I
think that is ok already).

2013/10/2 Stefan van der Walt notifications@github.com

Is this what most people would want to use? If so, then yes.

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[stefanv]

We have the opportunity to start this deprecation before the 0.11 release, if you want.