[ncl-talk] convert polyline shapefile to netcdf via ncl_convert2nc
Dennis Shea
shea at ucar.edu
Mon Apr 9 19:58:28 MDT 2018
I'll take Dave's example a bit further.
Given that count, valavg and freq have coordinate variables. [Please read.]
Variable: count
Number of Dimensions: 2
Dimensions and sizes: [lat | 11] x [lon | 19]
Coordinates:
lat: [ 0..50]
lon: [90..180]
Number Of Attributes: 3
units :
long_name : Occurrence Count: vMax=35
_FillValue : 1e+20
====================================================
test_lat = 20.0
test_lon = 130.0
print("---")
print("---> ("+test_lat+","+test_lon+")")
print("count ="+count({test_lat},{test_lon})) ; coordinate
subscripting {...}
print("valavg="+valavg({test_lat},{test_lon}))
print(" freq="+ freq({test_lat},{test_lon}))
print("---")
(0) ---> (20,130)
(0) count =86
(0) valavg=76.1047
(0) freq=7.83242
=========================================================
See attached
On Mon, Apr 9, 2018 at 7:12 PM, Dave Allured - NOAA Affiliate <
dave.allured at noaa.gov> wrote:
> Oops, there is a bug in my print statement. Change "lines" to "data":
>
> print (count(jl,il) + " " + data(n))
>
>
> On Mon, Apr 9, 2018 at 6:22 PM, Dave Allured - NOAA Affiliate <
> dave.allured at noaa.gov> wrote:
>
>> Lyndz,
>>
>> Try this to find the problem with your counting method. Below this line:
>>
>> valavg(jl,il) = valavg(jl,il) + cval(n)
>>
>> Add these code lines:
>>
>> test_lat = 20.0
>> test_lon = 130.0
>> jtest = toint((test_lat-latS)/dlat)
>> itest = toint((test_lon-lonW)/dlon)
>>
>> if (il .eq. itest .and. jl .eq. jtest) then
>> print (count(jl,il) + " " + lines(n))
>> end if
>>
>> In the code above, change test_lat and test_lon to the coordinates of any
>> single grid box that you want to check. Then run the program. This will
>> print every input record that gets counted for that one grid box.
>>
>> For example, I get 86 counts for the grid box example above, i..e. 20N,
>> 130E.
>>
>> --Dave
>>
>>
>> On Sun, Apr 8, 2018 at 9:04 PM, Lyndz <olagueralyndonmark429 at gmail.com>
>> wrote:
>>
>>> Hi Sir Dennis,
>>>
>>> I tried your suggestion. I was able to run the script but I'm getting a
>>> very large count. When I counted it manually, the count does not exceed 10.
>>> But I'm getting around 88.
>>> Attached are the output image, csv input file, and modified script.
>>>
>>> I only wanted to count the TC with Vmax greater than 35knts. So I tried
>>> masking first the data.
>>>
>>> I might be missing one important step here.
>>>
>>> Many thanks for the help.
>>>
>>> Sincerely,
>>>
>>> Lyndz
>>>
>>>
>>> On Mon, Apr 9, 2018 at 3:17 AM, Dennis Shea <shea at ucar.edu> wrote:
>>>
>>>> http://www.ncl.ucar.edu/Applications/binning.shtml
>>>>
>>>> See Example 2:
>>>>
>>>> freq = count
>>>> freq = (count/npts)*100 ; comment this
>>>>
>>>>
>>>> On Sat, Apr 7, 2018 at 9:05 PM, Lyndz <olagueralyndonmark429 at gmail.com>
>>>> wrote:
>>>>
>>>>> Hi Sir Rick,
>>>>>
>>>>> Thank you for the fast response.
>>>>> I wanted to create a 5degree by 5degree grid NetCDF file from the
>>>>> shapefile, where each grid box contains the "count"(frequency) of unique TC
>>>>> tracks per category.
>>>>> I'm just wondering if this is possible to do in NCL.
>>>>>
>>>>> Sincerely,
>>>>>
>>>>> Lyndz
>>>>>
>>>>>
>>>>> On Sun, Apr 8, 2018 at 3:34 AM, Rick Brownrigg <brownrig at ucar.edu>
>>>>> wrote:
>>>>>
>>>>>> Hi Lyndz,
>>>>>>
>>>>>> I'm not sure there is a "correct" way to do this. NetCDF is really
>>>>>> good at representing regular arrays of data, whereas polylines/polygons
>>>>>> tend to have varying numbers of coordinate pairs -- what would lat and lon
>>>>>> variables look like in that case, and what would be the meaning of lat/lon
>>>>>> dimensions? NCL makes a shapefile *look* like a NetCDF file by packing the
>>>>>> coordinate information for all features into the x/y variables, but then
>>>>>> one has to utilize the geometry and segments variables to unpack
>>>>>> coordinates for each feature. The shapefiles examples page show many
>>>>>> examples of doing this:
>>>>>>
>>>>>> http://ncl.ucar.edu/Applications/shapefiles.shtml
>>>>>>
>>>>>> If you are working with NCL, you are probably better off leaving your
>>>>>> data as a shapefile*. *I take it however that you have other reasons
>>>>>> for wanting a NetCDF file?
>>>>>>
>>>>>> Finally, I might comment that the conversion result may not be
>>>>>> correct -- its suspect to me that the "num_points" value is exactly twice
>>>>>> the value of "num_features" -- I wonder if maybe just the end-points of the
>>>>>> tracks where what got captured in the conversion?
>>>>>>
>>>>>> Rick
>>>>>>
>>>>>> On Fri, Apr 6, 2018 at 11:30 PM, Lyndz <olagueralyndonmark429 at gmail.c
>>>>>> om> wrote:
>>>>>>
>>>>>>> Dear NCL experts,
>>>>>>>
>>>>>>> I would like to convert the following shapefile to a netcdf file.
>>>>>>> I created the shapefile from a csv file containing jtwc tc tracks
>>>>>>> (see attached csv2shp.py)
>>>>>>> Also attached is the csv file.
>>>>>>>
>>>>>>> When I used the ncl_convert2nc the netcdf file has no lat-lon
>>>>>>> dimension. Here's the output of the ncdump. Is it also possible to divide
>>>>>>> the TC categories by dividing the Vmax values?
>>>>>>>
>>>>>>> I'll appreciate any suggestion on how to do this correctly.
>>>>>>>
>>>>>>> netcdf par_jtwc_above_ts_1979-1993 {
>>>>>>> dimensions:
>>>>>>> geometry = 2 ;
>>>>>>> segments = 2 ;
>>>>>>> num_features = 1050 ;
>>>>>>> num_segments = 1050 ;
>>>>>>> num_points = 2100 ;
>>>>>>> variables:
>>>>>>> int geometry(num_features, geometry) ;
>>>>>>> int segments(num_segments, segments) ;
>>>>>>> double x(num_points) ;
>>>>>>> double y(num_points) ;
>>>>>>> int SN(num_features) ;
>>>>>>> int CY(num_features) ;
>>>>>>> int Y1(num_features) ;
>>>>>>> int M1(num_features) ;
>>>>>>> int D1(num_features) ;
>>>>>>> int H1(num_features) ;
>>>>>>> int VMax1(num_features) ;
>>>>>>> int Y2(num_features) ;
>>>>>>> int M2(num_features) ;
>>>>>>> int D2(num_features) ;
>>>>>>> int H2(num_features) ;
>>>>>>> int VMax2(num_features) ;
>>>>>>>
>>>>>>> // global attributes:
>>>>>>> :segs_numPnts = 1 ;
>>>>>>> :segs_xyzIndex = 0 ;
>>>>>>> :geom_numSegs = 1 ;
>>>>>>> :geom_segIndex = 0 ;
>>>>>>> :geometry_type = "polyline" ;
>>>>>>> :layer_name = "par_jtwc_above_ts_1979-1993" ;
>>>>>>> :creation_date = "Sat Apr 7 14:11:24 JST 2018" ;
>>>>>>> :NCL_Version = "6.4.0" ;
>>>>>>> :system = "Linux localhost.localdomain 3.10.0-327.36.3.el7.x86_64 #1
>>>>>>> SMP Mon Oct 24 16:09:20 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux" ;
>>>>>>> :Conventions = "None" ;
>>>>>>> :title = "NCL: convert-OGR-to-netCDF" ;
>>>>>>> }
>>>>>>>
>>>>>>> Sincerely,
>>>>>>>
>>>>>>> Lyndz
>>>>>>>
>>>>>>
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