Computes the inverse of `rfftn`. This function computes the inverse of the N-dimensional discrete Fourier Transform for real input over any number of axes in an M-dimensional array by means of the Fast Fourier Transform (FFT). In other words, ``irfftn(rfftn(a), a.shape) == a``
(a, s=None, axes=None, norm=None)
| 1259 | |
| 1260 | @array_function_dispatch(_fftn_dispatcher) |
| 1261 | def irfftn(a, s=None, axes=None, norm=None): |
| 1262 | """ |
| 1263 | Computes the inverse of `rfftn`. |
| 1264 | |
| 1265 | This function computes the inverse of the N-dimensional discrete |
| 1266 | Fourier Transform for real input over any number of axes in an |
| 1267 | M-dimensional array by means of the Fast Fourier Transform (FFT). In |
| 1268 | other words, ``irfftn(rfftn(a), a.shape) == a`` to within numerical |
| 1269 | accuracy. (The ``a.shape`` is necessary like ``len(a)`` is for `irfft`, |
| 1270 | and for the same reason.) |
| 1271 | |
| 1272 | The input should be ordered in the same way as is returned by `rfftn`, |
| 1273 | i.e. as for `irfft` for the final transformation axis, and as for `ifftn` |
| 1274 | along all the other axes. |
| 1275 | |
| 1276 | Parameters |
| 1277 | ---------- |
| 1278 | a : array_like |
| 1279 | Input array. |
| 1280 | s : sequence of ints, optional |
| 1281 | Shape (length of each transformed axis) of the output |
| 1282 | (``s[0]`` refers to axis 0, ``s[1]`` to axis 1, etc.). `s` is also the |
| 1283 | number of input points used along this axis, except for the last axis, |
| 1284 | where ``s[-1]//2+1`` points of the input are used. |
| 1285 | Along any axis, if the shape indicated by `s` is smaller than that of |
| 1286 | the input, the input is cropped. If it is larger, the input is padded |
| 1287 | with zeros. If `s` is not given, the shape of the input along the axes |
| 1288 | specified by axes is used. Except for the last axis which is taken to |
| 1289 | be ``2*(m-1)`` where ``m`` is the length of the input along that axis. |
| 1290 | axes : sequence of ints, optional |
| 1291 | Axes over which to compute the inverse FFT. If not given, the last |
| 1292 | `len(s)` axes are used, or all axes if `s` is also not specified. |
| 1293 | Repeated indices in `axes` means that the inverse transform over that |
| 1294 | axis is performed multiple times. |
| 1295 | norm : {"backward", "ortho", "forward"}, optional |
| 1296 | .. versionadded:: 1.10.0 |
| 1297 | |
| 1298 | Normalization mode (see `numpy.fft`). Default is "backward". |
| 1299 | Indicates which direction of the forward/backward pair of transforms |
| 1300 | is scaled and with what normalization factor. |
| 1301 | |
| 1302 | .. versionadded:: 1.20.0 |
| 1303 | |
| 1304 | The "backward", "forward" values were added. |
| 1305 | |
| 1306 | Returns |
| 1307 | ------- |
| 1308 | out : ndarray |
| 1309 | The truncated or zero-padded input, transformed along the axes |
| 1310 | indicated by `axes`, or by a combination of `s` or `a`, |
| 1311 | as explained in the parameters section above. |
| 1312 | The length of each transformed axis is as given by the corresponding |
| 1313 | element of `s`, or the length of the input in every axis except for the |
| 1314 | last one if `s` is not given. In the final transformed axis the length |
| 1315 | of the output when `s` is not given is ``2*(m-1)`` where ``m`` is the |
| 1316 | length of the final transformed axis of the input. To get an odd |
| 1317 | number of output points in the final axis, `s` must be specified. |
| 1318 |
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