[yt-users] Derivative Error

[Matthew Turk]

Hi Nathan,

How are you centering the slice?  This looks somewhat like a
difference in the centering.  Can you try something like:

pc = PlotCollection(pf, 'c')
pc.add_slice("GravGradient", "x")
pc.save()

for both the old and new, and see if they look similar?

-Matt

On Thu, Jun 14, 2012 at 1:41 PM, Nathan Butcher <butchernate at gmail.com> wrote:
> The colorbar scaling is similar, and the values have changed. It could be a
> large shift. It is hard for me to tell from the plot. I have attached the
> updated plot.
>
> Nathan
>
>
> On Thu, Jun 14, 2012 at 1:32 PM, Matthew Turk <matthewturk at gmail.com> wrote:
>>
>> On Thu, Jun 14, 2012 at 1:31 PM, Nathan Butcher <butchernate at gmail.com>
>> wrote:
>> > Hello Matt,
>> >
>> > Thanks, that seems to have done fixed the issue. I am seeing that the
>> > graph
>> > looks very different now compared to before. Would forgetting the extra
>> > zone
>> > change the appearance of the overall plot beyond edge effects?
>>
>> It should shift the derivative considerably, but the only other
>> differences should be at the edges.  Are the actual values different,
>> or is the colorbar scaling differently now?
>>
>> >
>> > Thank you,
>> > Nathan Butcher
>> >
>> >
>> > On Thu, Jun 14, 2012 at 1:21 PM, Matthew Turk <matthewturk at gmail.com>
>> > wrote:
>> >>
>> >> Hi Nathan,
>> >>
>> >> Yup, I agree with your assessment -- there's an edge effect.  You need
>> >> one more thing to get the derivative field working; you need to tell
>> >> yt to give you an extra zone in each direction.  You can do that by
>> >> changing your decorator for the derived field to:
>> >>
>> >> @derived_field(name = "GravGradientX", validators =
>> >> [ValidateSpatial(1)])
>> >>
>> >> I don't believe you need any additional changes inside the source
>> >> code.  Let us know if that fixes it!
>> >>
>> >> -Matt
>> >>
>> >> On Thu, Jun 14, 2012 at 1:14 PM, Nathan Butcher <butchernate at gmail.com>
>> >> wrote:
>> >> > Hello,
>> >> >
>> >> > Using an Enzo dataset, I have written a function to find the
>> >> > derivative
>> >> > in
>> >> > the x-direction of a field. When I try to plot the derivative, I see
>> >> > lines
>> >> > that throughout the plot that I'm guessing are due to the edges of
>> >> > cells.
>> >> > The attached plot is a slice of the x-direction derivative of the
>> >> > PotentialField viewed down the x-axis, but this error appears in
>> >> > plots
>> >> > for
>> >> > density and pressure as well. I am new to using yt, and I am not sure
>> >> > what
>> >> > is causing this.
>> >> >
>> >> > Thank you,
>> >> > Nathan Butcher
>> >> >
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