[ncl-talk] animation: delete polyline from plot ?

[Rick Brownrigg]

Hi Karin,

Rather than use gns_add_polyline, which associates the line with the plot,
what about gsn_polyline, which just graphically overlays the line.  I think
I was able to achieve something like what you are after with the attached
script. The essence of the drawing is this:

  deltaLon = (lon2 - lon1) / 5.
  deltaLat = (lat2 - lat1) / 5.
  do i=0,4
     draw(plot1)
     gsn_polyline(wks, plot1, (/lon1+deltaLon*i, lon1+deltaLon*(i+1)/),   \
                             (/lat1+deltaLat*i, lat1+deltaLat*(i+1)/),   \
                 pres)
     frame(wks)
  end do

Hope that helps...
Rick

On Fri, May 20, 2016 at 3:50 PM, Karin Meier-Fleischer <
meier-fleischer at dkrz.de> wrote:

> Hi,
>
> is it possible to delete a polyline added to a simple map plot by
> gsn_add_polyline after it was drawn?
>
> I have flight trace data consisting of many segments per flight which I
> am animating segment by segment. This is not a problem. The idea now is
> to delete the first two segments after drawing 3 segments and further on
> to simulate a moving trace part to the end point (like a disappearing
> trail).
>
> The following snippet will cause an error:
>
> do n=0,nsegemnts-1
>     str = unique_string("trace")
>     map@$str$ =
> gsn_add_polyline(wks,map,(/x(n-1),x(n)/),(/y(n-1),y(n)/),pres)
>
>     if(n .gt. 2) then
>        trold0 = "trace"+(n-3)
>        trold1 = "trace"+(n-2)
>        delete([/map@$trold0$,map@$trold1$/])
>     end if
>
> end do
>
> warning:TransformPostDraw: tfPolyDrawList element 0 is invalid
> warning:TransformPostDraw: tfPolyDrawList element 1 is invalid
> warning:Attempt to reference attribute (trace1) which is undefined
>
>
> Due to the huge number of segments I would want to 'switch' the first
> segments off, if possible, and not to draw each single plot from scratch
> again for each flight .
>
> Bye,
> Karin
>
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