[ncl-talk] Issue with gsn_add_polyline

[David Brown]

Hi Andy,

You have indeed found a bug. The line between points 5 and 6 in the
left plot should take the shortest path not the long way around. A
work-around for that particular set of points would be to substitute
-1 for 359 in the first lon array.

But that should not be necessary. This will be fixed for the next
release, in fact right away.  If you need a fixed version prior to the
release let us know.
 -dave


On Wed, Apr 12, 2017 at 5:06 PM, Andy <awmiller at mit.edu> wrote:
> Hi,
> I am using NCL version 6.3.0. I am trying to use gsn_add_polyline to draw on
> a stereo-polar map (similar to the points added in example scatter_6.ncl). I
> attached a script that is hopefully showing the problem I am dealing with.
> Plot 1 (on the left) shows the data I originally wanted to plot.
> Unfortunately, the 5th and 6th point (counting from the NP to lower
> latitudes) are not connected on the shortest path. I then changed the value
> for the 6th point from 359 to 1 degrees, which resulted in plot 2. Thinking
> that gsn_add_polyline couldn't handle points on either side of 0/360, I made
> up data that with points alternating from 320-350 and 20-50. The resulting
> plot 3 does not show the same issue as plot 1. Can someone explain to me
> when gsn_add_polyline will connect points through 0 or what I am doing wrong
> here?
> Thanks,
> Andy
>
> --
> Andy Miller
> MIT PAOC PhD Candidate
>
> 77 Massachusetts Ave | 54-1715
> Cambridge, MA 02139
>
> Phone: 617-253-3715
> Email: awmiller at mit.edu
>
>
> _______________________________________________
> ncl-talk mailing list
> ncl-talk at ucar.edu
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>