[ncl-talk] Problem masking lat-lon points from a csv file using a shapefile

[Mary Haley]

Whoops, wrong PNG! Here's the correct one.

--Mary


On Tue, Oct 9, 2018 at 4:06 PM, Mary Haley <haley at ucar.edu> wrote:

> Lyndz,
>
> I'm going through some old emails and didn't see a response to this one.
>
> You were almost there, but in order to mask lat/lon values against one or
> more shapefile outlines, you must provide a data array that has the lat/lon
> arrays attached to it.
>
> Since you don't have a data array associated with your lat/lon pairs, you
> can simply create a dummy array, and then attach the lat/lon to it.  For
> example:
>     data1d=asciiread("jma.csv",-1,"float")
>     shp_filename="Bicol_region.shp"
>     print_shapefile_info(shp_filename)
>     lat = data1d(0::2)
>     lon = data1d(1::2)
>
> ;---Create dummy data array so we can attach lat/lon attributes to it.
>
>     npts = dimsizes(lat)
>     data = new(npts,float)
>     data at lat1d = lat
>     data at lon1d = lon
>
> ;---Return a mask array (0s and 1s) indicating which lat/lon pairs fall
> inside the shapefile region
>     opt = True
>     opt at return_mask = True
>     data_mask = shapefile_mask_data(data,shp_filename,opt)
>
> I've attached a full script that creates a plot and draws all the lat/lon
> pairs in red, with the ones inside the shapefile regions (only two of them)
> in blue.
>
> --Mary
>
>
>
>
> On Thu, Sep 13, 2018 at 1:51 AM, Lyndz <olagueralyndonmark429 at gmail.com>
> wrote:
>
>> Hello,
>>
>> I am trying to filter Tropical Cyclone (TC) lat-lon points from a csv
>> file using a shapefile and display the tracks.
>>
>> I'm reading the csv file and shapefile like this:
>>
>>     data=asciiread("jma.csv",(/1519,2/),"float")
>>     load "./shapefile_utils.ncl"
>>     shp_filename="Bicol_region.shp"
>>     data_mask    = shapefile_mask_data(data,shp_filename,True)
>>
>> Error: shapefile_mask_data: Error: not a valid rectilinear, curvilinear,
>> or uns
>> tructured grid
>>
>> I think I am missing a step after reading the csv file. Attached are the
>> shapefile and csv file.
>>
>> Any suggestions on how to do this correctly in NCL?
>>
>> Sincerely,
>>
>> Lyndz
>>
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>
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