[ncl-talk] Issue with creating a bar chart plot

[Rick Brownrigg]

I took a quick look at the code. As the errors indicate, it's happening in
a function call get_bart_width(). The calculation of the variable "delta"
is clearly wrong, and that sets off the warning, and triggers the error
later in get_bar_arrays about non-monotonicity (it's actually not that the
array is non-monotonic, it's that it has negative widths).

Beyond that, I can not tell why the calculation is wrong, particularly
without the data. That part of the code hasn't changed in some years, so
the v6.5.0 vs v6.6.2 difference is a mystery.

FWIW...
Rick


On Sun, Jun 7, 2020 at 6:58 PM Andrew Kren - NOAA Affiliate via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> I looked into these things. My x_axis is simply created this way:
>
> x_axis = ispan(4,73,3)
>
>
> And the printed values are correct, increasing by 3 starting at 4, 7, etc.
>
>
> So this is still kinda confusing as to why.
>
> On Sun, Jun 7, 2020 at 5:41 PM Dave Allured - NOAA Affiliate <
> dave.allured at noaa.gov> wrote:
>
>> It is only the horizontal axis that needs to be monotonically
>> increasing.  That is probably what the error message is about.  Naturally,
>> the vertical access may fluctuate anywhere.  You might want to check the
>> values of x_axis in your code to see if they make sense.
>>
>> Meanwhile, you should be able to insert a quick fix for x_axis with
>> temporary arrays, something like this.  This assumes that x_axis is
>> strictly decreasing rather than increasing.  If you change the order, then
>> you must also change the order for the vertical axis data, in the same
>> way.  X and Y values are supposed to form ordered pairs to make the bar
>> chart.
>>
>> xplot = x_axis(::-1)
>> yplot = tolong (temperature_top(i,23:0:-1))
>> plot = gsn_csm_xy (wks, xplot, yplot, res)
>>
>> I have no idea what changed to cause a newer NCL version to change from
>> the original behavior.
>>
>>
>> On Sun, Jun 7, 2020 at 1:57 PM Andrew Kren - NOAA Affiliate via ncl-talk <
>> ncl-talk at mailman.ucar.edu> wrote:
>>
>>> Dear ncl-talk,
>>>
>>> I upgraded my NCL to the latest version. Previously I was using version
>>> 6.5. When I upgraded, one of my ncl codes no longer runs successfully but
>>> creates an error code. I am creating a bar chart with gsn_csm_xy. I
>>> originally did not get these errors so I am unsure what could be going on.
>>> I tried to debug the issue but to no avail. Here are my errors:
>>>
>>> (0) get_bar_widths: Warning: The bar width(s) you selected (0.75) is
>>> larger than the smallest delta (-11).
>>>
>>> (0) Defaulting to -11.
>>>
>>> (0) get_bar_arrays: Fatal: The array is not monotonically increasing.
>>>
>>> (0) Cannot draw a bar chart.
>>>
>>> fatal:Illegal right-hand side type for assignment
>>>
>>>
>>> I checked that my array I am plotting has all correct values, and it
>>> does. I didn't know a bar chart had to have monotonically increasing
>>> values. Is there a way around this?
>>>
>>>
>>> The code where it fails is below, in the call to plot.
>>>
>>>
>>> plot = gsn_csm_xy(wks,x_axis,tolong(temperature_top(i,0:23)),res)
>>>
>>> Thanks,
>>>
>>> --
>>> Andrew Kren
>>> Meteorologist
>>> US Dept of Commerce
>>> National Oceanic and Atmospheric Administration
>>> National Weather Service Raleigh, NC
>>> 1005 Capability Drive, Suite 300
>>> Centennial Campus
>>> Raleigh, NC 27606-5226
>>>
>>
>
> --
> Andrew Kren
> Meteorologist
> US Dept of Commerce
> National Oceanic and Atmospheric Administration
> National Weather Service Raleigh, NC
> 1005 Capability Drive, Suite 300
> Centennial Campus
> Raleigh, NC 27606-5226
>
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