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

[Lyndz]

Dear Mary,

Thank you so much for this.

Lyndz



On Wed, Oct 10, 2018 at 7:08 AM Mary Haley <haley at ucar.edu> wrote:

> 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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