[pyngl-talk] Possible to plot on map without filling polygons ?

Xiaoni Wang xiaoni.wang at obspm.fr
Mon Nov 6 06:17:28 MST 2017

Hi Dear Mary,
     Thank you for your explanation. (Excuse me for my late response).

     I have another question. I have some 1D data irregularly distributed over a region. I would like to plot these data on a 2D map, without gridding, without filling polygons or triangles. I just would like to show data in different colors (given different values) at their lat/lon locations. 
     For your information, it is over a small region (3 by 3 degree for the latitude/longitude range), and number of data is not enormous over the region. I tried contour_map with resources.cnFillOn=True, resources.cnFillMode=RasterFill;  and it works. But it used TriangularMesh. If I set resources.cnFillOn=False, then it  produces no points or color on the map. If you have any suggestion, then I would appreciate !

      PS: If there is no way to display as I wished, then I would like just to add the data locations on the contour_map. Thanks in advance for your help.

Best regards

Le 27 oct. 2017 à 00:37, Mary Haley <haley at ucar.edu> a écrit :

> Xiaoni,
> I'm sorry for the delay. I didn't realize there was an unanswered question.
> When you say "specific value with white color" do you mean that you want to color a 0-level contour line in white, or that you want to specify a contour *fill* for values equal to 0?
> As an example of specifying a particular color for a contour line, see spaghetti.py at:
> http://www.pyngl.ucar.edu/Examples/gallery.shtml
> This uses only one contour level, and sets the color for this level using cnLineColor and an index value:
> res.cnLevelSelectionMode = "ExplicitLevels" # explicit contour levels
> res.cnLevels             = 5500             # which level(s) to plot
> res.cnLineColor          = 1      # index 1 in default color table. Can also 
>                                   # use a named color, like "white"        
> If you want to set multiple levels with multiple colors, then provide an array of values to cnLevels, and use cnLineColors to set the color for each.
> If you want to set the colors for filling between contour levels, then you can use cnFillColors. See example hdf3.py, which does this with:
> res.cnLevelSelectionMode = "ExplicitLevels"
> res.cnLevels             = [0.01,0.02,0.04,0.08,0.16,0.32,0.64, 0.96]
> res.cnFillColors         = ["white","cyan", "green","yellow",
>                             "darkorange","red","magenta","purple","black"]
> --Mary
> On Thu, Oct 19, 2017 at 3:41 AM, Xiaoni Wang <xiaoni.wang at obspm.fr> wrote:
> Hi all,
>      May I ask how to plot a specific value (0 for example) with white color by using NGL in a 2D contour plot ? Thank you in advance !
> Best wishes,
> Xiaoni Wang
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