[yt-users] How to use if, elif, else statements in creating a derived field
Reju Sam John
rejusamjohn at gmail.com
Sun Oct 27 01:02:57 PDT 2013
Still white patches are coming. I don't know what's the problem.
On Sun, Oct 27, 2013 at 11:46 AM, Reju Sam John <rejusamjohn at gmail.com>wrote:
> Thanks nathan and suoqing..... Let me try with your suggestions....
>
>
> On Sun, Oct 27, 2013 at 11:37 AM, Nathan Goldbaum <nathan12343 at gmail.com>wrote:
>
>> And using suoqing's example, I can control whether or not we should take
>> the logarithm of a variable in plots:
>>
>> @derived_field(name = "MyField", take_log=False)
>> def my_new_field(field, data):
>> tmp_data = (data["MachNumber"] <= 2) * (.5 * data["MachNumber"]**2. -
>> 1)
>> tmp_data = tmp_data + (data["MachNumber"] > 2) * (data["MachNumber"]
>> <= 100) * ((.5* (data["MachNumber"])**4) + (.5* (data["MachNumber"])**3))
>> tmp_data = tmp_data + (data["MachNumber"] > 100) * 5.446361E-01
>> return tmp_data
>>
>> If you've already created a plot, you can also disable field logging like
>> so:
>>
>> slc = SlicePlot(pf, 0, 'Density')
>> slc.set_log('Density', False)
>>
>> -Nathan
>>
>>
>> On Sat, Oct 26, 2013 at 11:02 PM, Suoqing JI <jisuoqing at gmail.com> wrote:
>>
>>> Hi Reju,
>>>
>>> The first thing occurs to me is that the area of white patch contains no
>>> positive field value, so it can not be plotted in log scale.
>>>
>>> Also, about the way of defining a derived field, I might prefer the
>>> following way, for example:
>>>
>>> @derived_field(name = "MyField")
>>> def my_new_field(field, data):
>>> tmp_data = (data["MachNumber"] <= 2) * (.5 * data["MachNumber"]**2.
>>> - 1)
>>> tmp_data = tmp_data + (data["MachNumber"] > 2) * (data["MachNumber"]
>>> <= 100) * ((.5* (data["MachNumber"])**4) + (.5* (data["MachNumber"])**3))
>>> tmp_data = tmp_data + (data["MachNumber"] > 100) * 5.446361E-01
>>> return tmp_data
>>>
>>> Best wishes,
>>> Suoqing
>>>
>>> On Oct 26, 2013, at 10:27 PM, Reju Sam John <rejusamjohn at gmail.com>
>>> wrote:
>>>
>>> Dear Matt,
>>> Thanks for the help. Now my problem with the code solved. But the slice
>>> plot of the new field has some problem -- white patch are coming as shown
>>> below. What may be the reason?
>>> <output.png>
>>>
>>>
>>> On Sat, Oct 26, 2013 at 7:59 PM, Matthew Turk <matthewturk at gmail.com>wrote:
>>>
>>>> Hi Reju,
>>>>
>>>> On Sat, Oct 26, 2013 at 2:50 AM, Reju Sam John <rejusamjohn at gmail.com>
>>>> wrote:
>>>> > Dear Kacper,
>>>> >
>>>> > My logic was wrong, and yours is right. But with the following code
>>>> >
>>>> > @derived_field(name = "MyField")
>>>> > def my_new_field(field, data):
>>>> > temp = data["MachNumber"].copy().fill(5.446361E-01)
>>>> > #print temp
>>>> >
>>>> > ind = np.where(data["MachNumber"] < 2)
>>>> > temp[ind] = 1.9564E-3*((data["MachNumber"][ind]**2) - 1)
>>>> > ind = np.where((data["MachNumber"] >= 2) and (data["MachNumber"])
>>>> < 100)
>>>> > temp[ind] =
>>>> >
>>>> (5.699327E-1*((data["MachNumber"][ind]-1)**4))/(data["MachNumber"][ind]**4)
>>>> > - (3.337557E-1*
>>>> > ((data["MachNumber"][ind]-1)**3))/((data["MachNumber"][ind])**4) +
>>>> > (4.173271E+0*
>>>> > ((data["MachNumber"][ind]-1)**2))/((data["MachNumber"][ind])**4) -
>>>> > (9.775620E+0*
>>>> ((data["MachNumber"][ind]-1)))/((data["MachNumber"][ind])**4)+
>>>> > 5.455605E+0/(data["MachNumber"][ind])**4
>>>> > return temp
>>>> >
>>>> > I am getting this Traceback
>>>> >
>>>> > line 41, in my_new_field
>>>> > temp[ind] = 1.9564E-3*((data["MachNumber"][ind]**2) - 1)
>>>> > TypeError: 'NoneType' object does not support item assignment
>>>> >
>>>> > Would you suggest any solution?
>>>>
>>>> I believe the problem is in your .fill() statement. That doesn't
>>>> return an array, so you need to do it after the assignment. For
>>>> instance:
>>>>
>>>> temp = data["MachNumber"].copy()
>>>> temp.fill(5.446361E-01)
>>>>
>>>> -Matt
>>>>
>>>> >
>>>> >
>>>> >
>>>> > On Mon, Oct 21, 2013 at 2:58 PM, Kacper Kowalik <
>>>> xarthisius.kk at gmail.com>
>>>> > wrote:
>>>> >>
>>>> >> On 10/21/2013 11:10 AM, Reju Sam John wrote:
>>>> >> > Dear all,
>>>> >> >
>>>> >> > I would like to create a derived field which should return a value
>>>> >> > according to specified conditions. My definition of new field is
>>>> shown
>>>> >> > below.. But it is giving error.
>>>> >> >
>>>> >> >
>>>> >> > @derived_field(name = "MyField")
>>>> >> > def my_new_field(field, data):
>>>> >> > if data.pf["MachNumber"] < 2 :
>>>> >> > return (.5* (data["MachNumber"])**2) - 1
>>>> >> > elif data.pf["MachNumber"] < 100 :
>>>> >> > return (.5* (data["MachNumber"])**4) + (.5*
>>>> >> > (data["MachNumber"])**3)
>>>> >> > else:
>>>> >> > return 5.446361E-01
>>>> >> >
>>>> >> >
>>>> >> >
>>>> >> > Please suggest me how to implement if, elif, else statements in
>>>> creating
>>>> >> > a
>>>> >> > derived field.
>>>> >>
>>>> >> Hi,
>>>> >> your derived fields looks fine (except for missing space in the
>>>> >> indentation of the last statement). Could you attach the backtrace?
>>>> >>
>>>> >> One thing that's confusing me is 'data.pf["MachNumber"]'. Do you
>>>> have a
>>>> >> global parameter with such name defined or you'd rather create a
>>>> MyField
>>>> >> based on local value of "MachNumber" field?
>>>> >> If the latter you could try something like this:
>>>> >>
>>>> >> @derived_field(name = "MyField")
>>>> >> def my_new_field(field, data):
>>>> >> temp = data["MachNumber"].copy().fill(5.446361E-01)
>>>> >> ind = np.where(data["MachNumber"] < 2)
>>>> >> temp[ind] = 0.5 * data["MachNumber"][ind] ** 2 - 1.0
>>>> >> ind = np.where((data["MachNumber"] >= 2) &
>>>> >> (data["MachNumber"]) < 100))
>>>> >> temp[ind] = 0.5 * data["MachNumber"][ind] ** 4 + \
>>>> >> 0.5 * data["MachNumber"][ind] ** 3
>>>> >> return temp
>>>> >>
>>>> >>
>>>> >> Cheers,
>>>> >> Kacper
>>>> >>
>>>> >>
>>>> >>
>>>> >> _______________________________________________
>>>> >> yt-users mailing list
>>>> >> yt-users at lists.spacepope.org
>>>> >> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
>>>> >>
>>>> >
>>>> >
>>>> >
>>>> > --
>>>> > Reju Sam John
>>>> >
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>>>
>>>
>>>
>>> --
>>> Reju Sam John
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>>
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>
>
> --
> Reju Sam John
>
--
Reju Sam John
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