python - Search elements in two arrays in the given range using numpy.where() -

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i'm working big arrays of geophysical data. have 2 numpy arrays have sizes 320x340: first xlat contains latitude of every point in grid, second xlon contains longitude of every point in grid. every i, j describes point on ground latitude xlat[i][j] , longitude xlon[i][j].

i have point coordinates p_lat , p_lon , have find closest 4 point given point.

first of wrote simple function run through point on x-axis , y-axis, makes 320*340 = 108 800 iterations , works very slow (~0.5 seconds every point):

    in range(0, lat-1):             j in range(0, lon-1):                      if st_lon >= xlon[i][j] , \                             st_lon < xlon[i][j + 1] , \                             st_lat >= xlat[i][j] , \                             st_lat < xlat[i + 1][j]:                             return (true, i, + 1, j, j + 1)

then found info numpy.where() , wrote code:

    in range(0, lat):             rows = numpy.where((xlon[i] >= st_lon - 0.5) & (xlon[i] <= st_lon + 0.5))          j in rows[0]:             if st_lon >= xlon[i][j] , \                             st_lon < xlon[i][j + 1] , \                             st_lat >= xlat[i][j] , \                             st_lat < xlat[i + 1][j]:                 return (true, i, + 1, j, j + 1)

this function works faster (~0.015 sec every point), don't think right , beautiful solution.

so final question how can find items in both arrays, satisfy conditions:

xlon[i] <= st_lon <= xlon[i][j+1] , xlat[i][j] <= st_lat <= xlat[i+1][j]

and should work quickly?

i not sure programming task, let me repeat in own words:

you have 2 2dim arrays xlat , xlon. kind of translating arrays latitude / longitude grid.

from code examples conclude: xlon[i][j]==xlon[h][j] valid i,h in range(0,lat) ?! (maybe there reason have object, doesn't performant)

so simple solution should treat bot dimensions seperately:

for in range(0, lat-1):     if (xlon[i][0] >= st_lon - 0.5) & (xlon[i][0] <= st_lon + 0.5):         break j in range(0, lon-1):     if (xlat[0][j] >= st_lat - 0.5) & (xlat[0][j] <= st_lat + 0.5)):         break    return (true, i, + 1, j, j + 1)

you can replace if-break statement np.where.

i not sure if got right. if answer not help, usefull supply small working example python code xlon, xlat reduced to, say, 5x4 dimensions.


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