the zero frequency term, * ``x[1:n//2]`` should contain the positive-frequency terms, * ``x[n//2 + 1:]`` should contain the negative-frequency terms, in increasing order starting from the most negative frequency. For an even number of input points, ``x[n//2]`` represents the sum of the values at the positive and negative Nyquist frequencies, as the two are aliased together. See `fft` for details. Parameters ---------- x : array_like Input array, can be complex. n : int, optional Length of the transformed axis of the output. If `n` is smaller than the length of the input, the input is cropped. If it is larger, the input is padded with zeros. If `n` is not given, the length of the input along the axis specified by `axis` is used. See notes about padding issues. axis : int, optional Axis over which to compute the inverse DFT. If not given, the last axis is used. norm : {"backward", "ortho", "forward"}, optional Normalization mode (see `fft`). Default is "backward". overwrite_x : bool, optional If True, the contents of `x` can be destroyed; the default is False. See :func:`fft` for more details. workers : int, optional Maximum number of workers to use for parallel computation. If negative, the value wraps around from ``os.cpu_count()``. See :func:`~scipy.fft.fft` for more details. plan : object, optional This argument is reserved for passing in a precomputed plan provided by downstream FFT vendors. It is currently not used in SciPy. .. versionadded:: 1.5.0 Returns ------- out : complex ndarray The truncated or zero-padded input, transformed along the axis indicated by `axis`, or the last one if `axis` is not specified. Raises ------ IndexError If `axes` is larger than the last axis of `x`. See Also -------- fft : The 1-D (forward) FFT, of which `ifft` is the inverse. ifft2 : The 2-D inverse FFT. ifftn : The N-D inverse FFT. Notes ----- If the input parameter `n` is larger than the size of the input, the input is padded by appending zeros at the end. Even though this is the common approach, it might lead to surprising results. If a different padding is desired, it must be performed before calling `ifft`. If ``x`` is a 1-D array, then the `ifft` is equivalent to :: y[k] = np.sum(x * np.exp(2j * np.pi * k * np.arange(n)/n)) / len(x) As with `fft`, `ifft` has support for all floating point types and is optimized for real input. Examples -------- >>> import scipy.fft >>> import numpy as np >>> scipy.fft.ifft([0, 4, 0, 0]) array([ 1.+0.j, 0.+1.j, -1.+0.j, 0.-1.j]) # may vary Create and plot a band-limited signal with random phases: >>> import matplotlib.pyplot as plt >>> rng = np.random.default_rng() >>> t = np.arange(400) >>> n = np.zeros((400,), dtype=complex) >>> n[40:60] = np.exp(1j*rng.uniform(0, 2*np.pi, (20,))) >>> s = scipy.fft.ifft(n) >>> plt.plot(t, s.real, 'b-', t, s.imag, 'r--') [, ] >>> plt.legend(('real', 'imaginary')) >>> plt.show() r