[yt-users] Variance in phase/profiles

[David Collins]

Matt and Britton--

Thanks for the input.  I'll poke around with both of those ideas and
let you know what I come up with.

Thanks!
d.

On Wed, Oct 5, 2011 at 10:13 AM, Matthew Turk <matthewturk at gmail.com> wrote:
> Hi Dave,
>
> I've thought about this on and off and there is an oustanding bug:
>
> https://bitbucket.org/yt_analysis/yt/issue/277/standard-deviation-for-1d-profiles
>
> One option is also to simply do it yourself by not using lazy_reader,
> and loading the data manually.  (Cameron has done this, sort of.)
> Another is to use a running-stddev algorithm, like one of those listed
> here:
>
> http://www.strchr.com/standard_deviation_in_one_pass
>
> If you want to look at this more in depth, please feel free to either
> ping yt-dev or leave comments in the ticket.  It'd be a great addition
> to have.
>
> -Matt
>
> On Wed, Oct 5, 2011 at 12:01 PM, Britton Smith <brittonsmith at gmail.com> wrote:
>> Hi Dave,
>>
>> The best I have been able to do for this is to manually bin up a 3d data
>> object with the cut_region function and then do the calculation myself bin
>> by bin.
>> For example, if you have a sphere, you can do
>> new_sphere = sphere.cut_region(['grid["Temperature"] > 1e5',
>> 'grid["Temperature"] < 1e6'])
>> That'll give you access to all the cells within that bin for a variance
>> calculation.  Note the quotes around those expressions.  The cuts are
>> applied in yt using eval functions.
>>
>> This will work, but it's slow and requires you to do a lot by hand.
>>
>> Britton
>>
>> On Wed, Oct 5, 2011 at 11:51 AM, david collins <antpuncher at gmail.com> wrote:
>>>
>>> Hi, Everybody!
>>>
>>> Does anyone out there have a technique for getting the variance out of
>>> a profile object?  A profile object is good at getting <X> vs. B, I'd
>>> then like to get < (X - <X>)^2 > vs B.  Matt and I had spittballed the
>>> possibility some time ago, but I was wondering if anyone out there had
>>> successfully done it.
>>>
>>> Thanks,
>>> d.
>>>
>>> --
>>> Sent from my computer.
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>>
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-- 
Sent from my computer.