[AstroPy] AstroPy Digest, Vol 81, Issue 12

Erik Tollerud erik.tollerud@gmail....
Thu Jun 20 12:17:20 CDT 2013


Hmm, ok, those seem like use-cases that overlap a lot with
astropy.table and astropy.io.ascii.  Do you find pandas is noticeably
faster than astropy.tables?

On Thu, Jun 20, 2013 at 12:50 PM, Chris Beaumont <beaumont@hawaii.edu> wrote:
> I thought I'd chime in on the pandas discussion :)
>
> I'm starting to use pandas a bit more in my day-to-day work. The two
> features most useful to me are:
>
> 1) Its file parsers are pretty robust and fast. I always try parsing CSV
> with pandas first
>
> 2) For tables tables with lots of categorical data, the grouping
> functionality is very nice. For example, calculations like "the mean age of
> each spectral type of star in my catalog" are usually one liners like
> df.groupby(['spectral_type']).age.mean. I spend a lot of time on the
> "split-apply-combine" page on the pandas docs
> (http://pandas.pydata.org/pandas-docs/stable/groupby.html).
>
> I won't speculate about whether that's enough an asset to warrant a
> dependency in astropy. I do agree that lots of other pandas features don't
> translate as well into astronomy use.
>
>
>
> On Thu, Jun 20, 2013 at 12:34 PM, Erik Tollerud <erik.tollerud@gmail.com>
> wrote:
>>
>> I'm of mixed minds about traits UI because once you know it you can make
>> great GUIs with it, but I've spent a lot of time troubleshooting people's
>> python installations to get traits to work.  That is, in general it can be
>> tricky to get installed because of all the dependencies.  Maybe this has
>> improved recently with Enthought's Canopy (or other new python distros), but
>> that's been my past experience.
>>
>> More generally, the view in the astropy core package is that we don't want
>> to put GUIs in the core because GUIs always carry lots of dependencies,
>> which we don't want to be forced to deal with.  But part of the whole reason
>> for affiliated packages was to get around this, so we're happy to see
>> GUI-based affiliated packages.
>>
>>
>> As for Pandas, to be totally honest, I don't see a huge amount to be
>> gained from adding a Pandas dependency Astropy.  It's honestly not clear
>> what it gives the astronomy community that numpy does not already have.  The
>> following quote from the Pandas web site has guided me to that conclusion:
>> "pandas helps fill this gap, enabling you to carry out your entire data
>> analysis workflow in Python without having to switch to a more domain
>> specific language like R."
>>
>> I have been carrying out my entire data analysis workflow for some time
>> now in python without using Pandas.  It looks to me like Pandas is a tool
>> that was written by and for statisticians who use R.  While we can take
>> lessons from this, it's not clear we get much out of it in an astronomy
>> context. For example, how would it make astropy's NDData, Quantity, or Table
>> better to use a Pandas DataFrame vs. a numpy array? Most of what we are
>> doing is building astronomy-convenient interfaces, and I'm not sure what
>> Pandas adds there, at the cost of a pretty heavy-weight dependency.
>>
>> It could just be that I don't know enough about Pandas, though.  So if
>> someone who knows Pandas better can speak to this, I'm all ears.
>>
>>
>>
>>
>> On Tue, Jun 18, 2013 at 3:35 PM, Thøger Rivera-Thorsen <trive@astro.su.se>
>> wrote:
>>>
>>> Pandas is a part of the newly-defined SciPy stack, after all, so that
>>> would be part of any science-oriented distribution worth its salt. In fact,
>>> I think it could be a good idea for astropy in general to use under the
>>> hood, but again, could clash with the philosophy of the project and possibly
>>> also maintainabillity.
>>>
>>> As for offering my code or just my experience, I'll have to square it
>>> with my supervisor first, and I also think it depends on what direction the
>>> project in question will take. I'm positive about the idea (which is why I
>>> wrote in the first place), but supervisor might think it is a better idea to
>>> actually get my paper in the project wrapped up before sending the code out
>>> there. Will get back about that one!
>>>
>>> /Emil
>>>
>>>
>>>
>>>
>>>
>>> On 2013-06-18 20:53, Slavin, Jonathan wrote:
>>>
>>> Hi Emil,
>>>
>>> That looks very nice!  I don't see Pandas as a big issue in terms of
>>> dependencies.  I don't know that much about traits, etc.  My thought about
>>> the gui was just based on my experience with matplotlib, and the fact that
>>> it is widely used -- though I would agree that too many dependencies can be
>>> a deterrent to people using something.  Are you offering your code as a
>>> starting point for the project?  It strikes me that many have gotten some
>>> sort of fitting package to a point of personal usability but no one has the
>>> time/interest/motivation to make a more generally usable package.
>>>
>>> Jon
>>>
>>> On Tue, Jun 18, 2013 at 2:34 PM, <astropy-request@scipy.org> wrote:
>>>>
>>>> Date: Tue, 18 Jun 2013 20:39:55 +0200
>>>> From: Th?ger Rivera-Thorsen <thoger.emil@gmail.com>
>>>> Subject: Re: [AstroPy] ESA Summer of Code in Space 2013
>>>> To: astropy@scipy.org
>>>> Message-ID: <51C0A97B.8090703@gmail.com>
>>>> Content-Type: text/plain; charset="iso-8859-1"
>>>>
>>>> I have been working on a fitting GUI for a while, although it is made
>>>> with a specific task in mind.
>>>> However, it is not based on Matplotlib but on Traits/Traitsui/Chaco and
>>>> Pandas. It is made for a specific projhect I'm working and as such not
>>>> yet usable for more general cases, but it could be a starting point, if
>>>> the dependencies don't conflict with astropy politics.
>>>>
>>>> Especially, I am happy about the choice of Pandas for managing a quite
>>>> complex data structure (the fitted and/or guessed values of an arbitrary
>>>> number of transitions for an arbitrary number of rows or collapsed rows
>>>> of a spatially resolved spectrum) of a), but also with the Traits-based
>>>> interactive interface to build complex line profiles from single
>>>> gaussians, good for fitting-by-eye and giving good initial guesses for
>>>> fitting of complex line profiles. It hooks directly up to a wrapper I've
>>>> made for lmfit, but given the modularity, it should be relatively easy
>>>> to change to other backends.
>>>>
>>>> It's still a work-in-progress, but there are some screenshots here:
>>>> http://flic.kr/s/aHsjGaEMGg .
>>>> I know the choice and number of dependencies may be prohibitive but it
>>>> saved a lot of work on the GUI, and Pandas means the difference between
>>>> sanity and madness when it comes to keeping track of so many parameters.
>>>>
>>>> Cheers,
>>>> Emil
>>>
>>>
>>>
>>>
>>> ________________________________________________________
>>> Jonathan D. Slavin                 Harvard-Smithsonian CfA
>>> jslavin@cfa.harvard.edu       60 Garden Street, MS 83
>>> phone: (617) 496-7981       Cambridge, MA 02138-1516
>>> fax: (617) 496-7577            USA
>>> ________________________________________________________
>>>
>>>
>>>
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>>
>>
>>
>> --
>> Erik
>>
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>
>
>
> --
> ************************************
> Chris Beaumont
> Graduate Student
> Institute for Astronomy
> University of Hawaii at Manoa
> 2680 Woodlawn Drive
> Honolulu, HI 96822
> www.ifa.hawaii.edu/~beaumont
> ************************************



-- 
Erik


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