[ncl-talk] BoxCenters in pyNGL

Tue Aug 21 16:22:40 MDT 2018

Hi Clint,

I've been looking into this and it appears to be a bug.

Normally, you are supposed to be able to set your own labels using
lbLabeStrings, but it appears that the contour object has to be in a
certain "state" (i.e. it has to have been created already) in order for the
labels to take effect.

A work-around is to use set_values, which allows you to apply resource
changes to an object that has already been created.

I've attached a modified contour2.py that creates two PNGs. The first PNG
is the plot with the bug. The second one is with the correct labels set
using "set_values".

BTW, this is not a PyNGL bug, but an internal NCL graphics bug. The reason
why you don't see this bug when you use NCL's gsn_csm_contour function is
because that function constructs the labelbar from scratch.

And a second BTW, PyNGL is now officially available under Python 3. I need
to update some documentation on this, but if you use conda, it should give
you the Python 3 version by default:

conda create --name pyn_env --channel conda-forge pyngl

I made a slight change to "contour2.py" so it would work under Python 3,
which was this line:

nrlist.lbLabelStrings = list(range(-30,110,10))

Under Python 2, it looked like this:

nrlist.lbLabelStrings = range(-30,110,10)

U
nder Python 3, the above line will give you the error:

  value for keyword lbLabelStrings is invalid.

Traceback (most recent call last):
  File "contour2.py", line 41, in <module>
    Ngl.set_values(contour,nrlist)
  File
"/Users/haley/miniconda3/envs/pyn_env_py3/lib/python3.6/site-packages/ngl/__init__.py",
line 5622, in set_values
    values = NhlSetValues(_int_id(obj),rlist)

SystemError: <built-in function NhlSetValues> returned NULL without setting
an error

Let me know if you continue to have problems with PyNGL. We are trying to
put more attention on this package to clean it up and feedback is very
useful!

Thanks,

--Mary

On Tue, Aug 21, 2018 at 7:00 AM, Clinton Rowe <crowe1 at unl.edu> wrote:

> Hi Mary,
>
>
>
> I upgraded to the latest pyNGL release and add lbLabelStrings to my code,
> and I still get the last box labeled with a generic label (Label_13), even
> though I have 14 labels defined.  On my first try, I accidentally used 30
> as my step size when generating the labels and that made no difference in
> how the labelbar was labeled.
>
>
>
> What am I missing here?
>
>
>
> Clint
>
>
>
> ========================================================
>
> Clinton M. Rowe
>
> Professor and Graduate Chair         phone:(402)472-1946
>
> Earth & Atmospheric Sciences           fax:(402)472-4917
>
> University of Nebraska- Lincoln           crowe1 at unl.edu
>
>
>
> *From:* Mary Haley <haley at ucar.edu>
> *Sent:* Thursday, August 16, 2018 7:28 PM
> *To:* Clinton Rowe <crowe1 at unl.edu>
> *Cc:* ncl-talk at ucar.edu
> *Subject:* Re: [ncl-talk] BoxCenters in pyNGL
>
>
>
> Hi Clint,
>
>
>
> Sorry for taking so long to get back to this. I'm slowing climbing my way
> back to normalcy after a few weeks of constant meetings.
>
>
>
> I'm wondering if this example has been fixed in the latest PyNGL, because
> it worked fine for me, although one label is missing because once you go to
> box centers, you have to provide an additional label. (You can add the
> extra label with lbLabelStrings.)
>
>
>
> I installed PyNGL and PyNIO with:
>
>
>
> conda create --name pyn_env --channel conda-forge pynio pyngl
>
>
>
> and then ran your attached script, with the resultant attached image.
>
>
> Do you know what version of PyNGL you're running? You can print
> "Ngl.__version__
>
> " for this information.
>
>
>
> --Mary
>
>
>
> On Fri, Aug 3, 2018 at 10:43 AM, Clinton Rowe <crowe1 at unl.edu> wrote:
>
> Mary, Rick, et al.,
>
>
>
> I transitioned a routine from NCL to pyNGL and the BoxCenters label
> resource is not working.  Labels are only drawn at alternate interior lines
> on the labelbar, rather than the box centers as desired.  As an example, I
> added one line to contour2.py to request labels at the center of the
> boxes.  I’ve attached the modified example and output png.
>
>
>
> Thanks,
>
> Clint
>
>
>
> ========================================================
>
> Clinton M. Rowe
>
> Professor and Graduate Chair         phone:(402)472-1946
>
> Earth & Atmospheric Sciences           fax:(402)472-4917
>
> University of Nebraska- Lincoln           crowe1 at unl.edu
>
>
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