I would like to find the nearest coord in a netcdf from a given latitude
and longitude.
I found some fantastic code that does this -
http://nbviewer.ipython.org/github/Unidata/unidata-python-workshop/blob/master/netcdf-by-coordinates.ipynb
but I keep receiving this error - I am receiving a ValueError: need more
than 1 value to unpack
I have pasted the code and full error below. Any help will be greatly
appreciated.
import numpy as np
import netCDF4
def naive_fast(latvar,lonvar,lat0,lon0):
# Read latitude and longitude from file into numpy arrays
latvals = latvar[:]
lonvals = lonvar[:]
ny,nx = latvals.shape
dist_sq = (latvals-lat0)**2 + (lonvals-lon0)**2
minindex_flattened = dist_sq.argmin() # 1D index of min element
iy_min,ix_min = np.unravel_index(minindex_flattened, latvals.shape)
return iy_min,ix_min
filename = "/Users/T_SFC.nc"
ncfile = netCDF4.Dataset(filename, 'r')
latvar = ncfile.variables['latitude']
lonvar = ncfile.variables['longitude']
iy,ix = naive_fast(latvar, lonvar, -38.009, 146.438)
print 'Closest lat lon:', latvar[iy,ix], lonvar[iy,ix]
ncfile.close()
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
/Applications/Canopy.app/appdata/canopy-1.3.0.1715.macosx-x86_64/Canopy.app/Contents/lib/python2.7/site-packages/IPython/utils/py3compat.pyc
in execfile(fname, *where)
202 else:
203 filename = fname
--> 204 __builtin__.execfile(filename, *where)
/Users/latlon_to_closestgrid.py in <module>()
22 lonvar = ncfile.variables['longitude']
23
---> 24 iy,ix = naive_fast(latvar, lonvar, -38.009, 146.438)
25 print 'Closest lat lon:', latvar[iy,ix], lonvar[iy,ix]
26 ncfile.close()
/Users/latlon_to_closestgrid.py in naive_fast(latvar, lonvar, lat0, lon0)
12 latvals = latvar[:]
13 lonvals = lonvar[:]
---> 14 ny,nx = latvals.shape
15 dist_sq = (latvals-lat0)**2 + (lonvals-lon0)**2
16 minindex_flattened = dist_sq.argmin() # 1D index of min element
ValueError: need more than 1 value to unpack
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