Apply function 'func' as a reduction across fields of a structured array. This is similar to `apply_along_axis`, but treats the fields of a structured array as an extra axis. The fields are all first cast to a common type following the type-promotion rules from `numpy.result_type`
(func, arr)
| 1180 | |
| 1181 | @array_function_dispatch(_apply_along_fields_dispatcher) |
| 1182 | def apply_along_fields(func, arr): |
| 1183 | """ |
| 1184 | Apply function 'func' as a reduction across fields of a structured array. |
| 1185 | |
| 1186 | This is similar to `apply_along_axis`, but treats the fields of a |
| 1187 | structured array as an extra axis. The fields are all first cast to a |
| 1188 | common type following the type-promotion rules from `numpy.result_type` |
| 1189 | applied to the field's dtypes. |
| 1190 | |
| 1191 | Parameters |
| 1192 | ---------- |
| 1193 | func : function |
| 1194 | Function to apply on the "field" dimension. This function must |
| 1195 | support an `axis` argument, like np.mean, np.sum, etc. |
| 1196 | arr : ndarray |
| 1197 | Structured array for which to apply func. |
| 1198 | |
| 1199 | Returns |
| 1200 | ------- |
| 1201 | out : ndarray |
| 1202 | Result of the recution operation |
| 1203 | |
| 1204 | Examples |
| 1205 | -------- |
| 1206 | |
| 1207 | >>> from numpy.lib import recfunctions as rfn |
| 1208 | >>> b = np.array([(1, 2, 5), (4, 5, 7), (7, 8 ,11), (10, 11, 12)], |
| 1209 | ... dtype=[('x', 'i4'), ('y', 'f4'), ('z', 'f8')]) |
| 1210 | >>> rfn.apply_along_fields(np.mean, b) |
| 1211 | array([ 2.66666667, 5.33333333, 8.66666667, 11. ]) |
| 1212 | >>> rfn.apply_along_fields(np.mean, b[['x', 'z']]) |
| 1213 | array([ 3. , 5.5, 9. , 11. ]) |
| 1214 | |
| 1215 | """ |
| 1216 | if arr.dtype.names is None: |
| 1217 | raise ValueError('arr must be a structured array') |
| 1218 | |
| 1219 | uarr = structured_to_unstructured(arr) |
| 1220 | return func(uarr, axis=-1) |
| 1221 | # works and avoids axis requirement, but very, very slow: |
| 1222 | #return np.apply_along_axis(func, -1, uarr) |
| 1223 | |
| 1224 | def _assign_fields_by_name_dispatcher(dst, src, zero_unassigned=None): |
| 1225 | return dst, src |