[Neuroimaging] Nibabel API change - always read as float

[Satrajit Ghosh]

hi ben,

i thought get_fdata() would always return float independent of whether the
data needs to be scaled or not. so in that sense a little different from
get_data, which would return datatype of disk if the data did not need to
be scaled, but float otherwise.

cheers,

satra

On Sun, Apr 23, 2017 at 9:25 AM, Ben Cipollini <bcipolli at ucsd.edu> wrote:

> My understanding of the discussion above was that get_fdata() would lead
> to the same behavior as get_data() now.
>
> On Sat, Apr 22, 2017 at 7:15 PM, Ariel Rokem <arokem at gmail.com> wrote:
>
>>
>>
>> On Tue, Apr 18, 2017 at 8:01 AM, Matthew Brett <matthew.brett at gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> On Wed, Jul 22, 2015 at 3:53 PM, Satrajit Ghosh <satra at mit.edu> wrote:
>>> > hi matthew,
>>> >
>>> >> I'm not sure what you mean by 'did not interpret this' unless you are
>>> >> agreeing with me that the niftiio library gives no clues as what the
>>> >> intention for the in-memory type was.  If anything I think that
>>> >> supports my reading that the authors had not considered the
>>> >> interpretation of "scl_slope != 0 -> in-memory float".
>>> >
>>> >
>>> > i simply meant they left any interpretation of how to scale or change
>>> of
>>> > in-memory data type to the end developer.
>>> >
>>> >> I can surely attach the raw scalefactors to the array proxy (dataobj),
>>> >
>>> >
>>> > that would be great
>>> >
>>> >>
>>> >> but I think it's a terrible idea to use the scl_slope == 0 as an
>>> >> indication for in-memory type, because it's not a convention that (as
>>> >> far as I know) anyone else uses,
>>> >
>>> >
>>> > all the examples of the code bases i provided in fact leave the
>>> in-memory
>>> > type to be the same as the native dtype for scalefactors (0, X) and
>>> (1, 0).
>>> > i agree, that this is an implementation of the standard as interpreted
>>> by
>>> > those developers, similar to present nibabel. i do agree that nifti
>>> authors
>>> > had nothing to say about such an interpretation.
>>>
>>> Following up on this one, much later - I have a new proposal, that I
>>> have written up here:
>>>
>>> https://github.com/nipy/nibabel/wiki/BIAP8
>>>
>>> Shortest possible summary:
>>>
>>> * add "get_fdata" method to images, returning floating point data;
>>> * deprecate "get_data" method in one year;
>>> * raise error for "get_data" method in three years.
>>>
>>>
>> Just to clarify: after the removal of "get_data", what would a user need
>> to do to produce the current behavior of a `get_data()` call?
>>
>> Something like this was mentioned somewhere along this thread:
>>
>> data = img.dataobj.get_unscaled()
>>
>> Is that it?
>>
>> This has the advantage that older code using nibabel will not silently
>>> return a different result, but will error, with an informative
>>> message, for the foreseeable future.
>>>
>>> Any thoughts on this version?
>>>
>>> Cheers,
>>>
>>> Matthew
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>>>
>>
>>
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>
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