# ValueError: zero-size array to reduction operation minimum which has no identity **URL:** \ **Category:** Python\ **Tags:** wradlib\ **Created:** [August 27, 2023, 4:22pm UTC](https://openradar.discourse.group/t/valueerror-zero-size-array-to-reduction-operation-minimum-which-has-no-identity/291 "2023-08-27T16:22:08Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![pikuljena](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/pikuljena/32/198_2.png) [@pikuljena](https://openradar.discourse.group/u/pikuljena)\ **Post date:** [August 27, 2023, 4:22pm UTC](https://openradar.discourse.group/t/valueerror-zero-size-array-to-reduction-operation-minimum-which-has-no-identity/291/1 "2023-08-27T16:22:08Z")
Hy i am trying to calculate beam blockage using srtm data . i am getting following error . code: rasterfile = “D:\FINAL YEAR PROJECT\Wradlib\gt30e060n40.dem” ds = wrl.io.open\_raster(rasterfile) rastervalues, rastercoords, proj = wrl.georef.extract\_raster\_dataset( ds, nodata=-32768.0 ) # Clip the region inside our bounding box ind = wrl.util.find\_bbox\_indices(rastercoords, rlimits) rastercoords = rastercoords[ind[1] : ind[3], ind[0] : ind[2], …] rastervalues = rastervalues[ind[1] : ind[3], ind[0] : ind[2]] # Map rastervalues to polar grid points polarvalues = wrl.ipol.cart\_to\_irregular\_spline( rastercoords, rastervalues, polcoords, order=3, prefilter=False ) error: ValueError Traceback (most recent call last) Cell In[8], line 15 12 rastervalues = rastervalues[ind[1] : ind[3], ind[0] : ind[2]] 14 # Map rastervalues to polar grid points —\> 15 polarvalues = wrl.ipol.cart\_to\_irregular\_spline( 16 rastercoords, rastervalues, polcoords, order=3, prefilter=False 17 ) File ~\anaconda3\envs\pyart\_env\lib\site-packages\wradlib\ipol.py:1690, in cart\_to\_irregular\_spline(cartgrid, values, newgrid, \*\*kwargs) 1687 nx = cartgrid.shape[1] 1688 ny = cartgrid.shape[0] → 1690 cxmin = np.min(cartgrid[…, 0]) 1691 cxmax = np.max(cartgrid[…, 0]) 1692 cymin = np.min(cartgrid[…, 1]) File ~\anaconda3\envs\pyart\_env\lib\site-packages\numpy\core\fromnumeric.py:2953, in min(a, axis, out, keepdims, initial, where) 2836 @array\_function\_dispatch(\_min\_dispatcher) 2837 def min(a, axis=None, out=None, keepdims=np.\_NoValue, initial=np.\_NoValue, 2838 where=np.\_NoValue): 2839 “”" 2840 Return the minimum of an array or minimum along an axis. 2841 (…) 2951 6 2952 “”" → 2953 return \_wrapreduction(a, np.minimum, ‘min’, axis, None, out, 2954 keepdims=keepdims, initial=initial, where=where) File ~\anaconda3\envs\pyart\_env\lib\site-packages\numpy\core\fromnumeric.py:88, in \_wrapreduction(obj, ufunc, method, axis, dtype, out, \*\*kwargs) 85 else: 86 return reduction(axis=axis, out=out, \*\*passkwargs) —\> 88 return ufunc.reduce(obj, axis, dtype, out, \*\*passkwargs) ValueError: zero-size array to reduction operation minimum which has no identity anybody have idea how to fix this ? ---
**Author:** ![kmuehlbauer](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/kmuehlbauer/32/439_2.png) [@kmuehlbauer](https://openradar.discourse.group/u/kmuehlbauer)\ **Post date:** [August 28, 2023, 6:17am UTC](https://openradar.discourse.group/t/valueerror-zero-size-array-to-reduction-operation-minimum-which-has-no-identity/291/2 "2023-08-28T06:17:41Z")
Hello @pikuljena, welcome to openradar discourse. I’m assuming a problem with `rlimits` not fitting your actual data projection. Can you please report the contents of `rlimits` you are using? The content of `proj` would also be interesting, to see which projection the DEM data is in. `rlimits` and `rastercoords` have to be in the same projection. ---
**Author:** ![pikuljena](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/pikuljena/32/198_2.png) [@pikuljena](https://openradar.discourse.group/u/pikuljena)\ **Post date:** [August 29, 2023, 12:48pm UTC](https://openradar.discourse.group/t/valueerror-zero-size-array-to-reduction-operation-minimum-which-has-no-identity/291/3 "2023-08-29T12:48:32Z")
rlimits (-0.9529142728897741, 74.71267576099122, 18.012914272889773, 79.00693742464783) rastercoords array([[[60.00416667, 39.99583333], [60.0125 , 39.99583333], [60.02083333, 39.99583333], …, [99.97916667, 39.99583333], [99.9875 , 39.99583333], [99.99583333, 39.99583333]], ``` [[60.00416667, 39.9875], [60.0125 , 39.9875], [60.02083333, 39.9875], ..., [99.97916667, 39.9875], [99.9875 , 39.9875], [99.99583333, 39.9875]], [[60.00416667, 39.97916667], [60.0125 , 39.97916667], [60.02083333, 39.97916667], ..., [99.97916667, 39.97916667], [99.9875 , 39.97916667], [99.99583333, 39.97916667]], ..., [[60.00416667, -9.97916667], [60.0125 , -9.97916667], [60.02083333, -9.97916667], ..., [99.97916667, -9.97916667], [99.9875 , -9.97916667], [99.99583333, -9.97916667]], [[60.00416667, -9.9875], [60.0125 , -9.9875], [60.02083333, -9.9875], ..., [99.97916667, -9.9875], [99.9875 , -9.9875], [99.99583333, -9.9875]], [[60.00416667, -9.99583333], [60.0125 , -9.99583333], [60.02083333, -9.99583333], ..., [99.97916667, -9.99583333], [99.9875 , -9.99583333], [99.99583333, -9.99583333]]]) ``` proj \ \> wkt = proj.ExportToWkt() ‘GEOGCS[“WGS 84”,DATUM[“WGS\_1984”,SPHEROID[“WGS 84”,6378137,298.257223563,AUTHORITY[“EPSG”,“7030”]],AUTHORITY[“EPSG”,“6326”]],PRIMEM[“Greenwich”,0,AUTHORITY[“EPSG”,“8901”]],UNIT[“degree”,0.0174532925199433,AUTHORITY[“EPSG”,“9122”]],AXIS[“Latitude”,NORTH],AXIS[“Longitude”,EAST],AUTHORITY[“EPSG”,“4326”]]’ ind (0, 6000, 0, 6000) after indexing rastercoords becomes an empty array ---
**Author:** ![kmuehlbauer](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/kmuehlbauer/32/439_2.png) [@kmuehlbauer](https://openradar.discourse.group/u/kmuehlbauer)\ **Post date:** [August 29, 2023, 1:23pm UTC](https://openradar.discourse.group/t/valueerror-zero-size-array-to-reduction-operation-minimum-which-has-no-identity/291/4 "2023-08-29T13:23:28Z")
> [@pikuljena](#): > > (-0.9529142728897741, 74.71267576099122, 18.012914272889773, 79.00693742464783) It looks like your rlimits is (latmin, lonmin, latmax, lonmax) but it should be (lonmin, latmin, lonmax, latmax) → (74.71267576099122, -0.9529142728897741, 79.00693742464783, 18.012914272889773). ---
**Author:** ![kmuehlbauer](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/kmuehlbauer/32/439_2.png) [@kmuehlbauer](https://openradar.discourse.group/u/kmuehlbauer)\ **Post date:** [October 27, 2023, 12:27pm UTC](https://openradar.discourse.group/t/valueerror-zero-size-array-to-reduction-operation-minimum-which-has-no-identity/291/5 "2023-10-27T12:27:09Z")