# scipy.fft.rfft¶

scipy.fft.rfft(x, n=None, axis=- 1, norm=None, overwrite_x=False, workers=None, *, plan=None)[source]

Compute the 1-D discrete Fourier Transform for real input.

This function computes the 1-D n-point discrete Fourier Transform (DFT) of a real-valued array by means of an efficient algorithm called the Fast Fourier Transform (FFT).

Parameters
xarray_like

Input array

nint, optional

Number of points along transformation axis in the input to use. 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.

axisint, optional

Axis over which to compute the FFT. If not given, the last axis is used.

norm{“backward”, “ortho”, “forward”}, optional

Normalization mode (see `fft`). Default is “backward”.

overwrite_xbool, optional

If True, the contents of x can be destroyed; the default is False. See `fft` for more details.

workersint, optional

Maximum number of workers to use for parallel computation. If negative, the value wraps around from `os.cpu_count()`. See `fft` for more details.

planobject, optional

This argument is reserved for passing in a precomputed plan provided by downstream FFT vendors. It is currently not used in SciPy.

New in version 1.5.0.

Returns
outcomplex ndarray

The truncated or zero-padded input, transformed along the axis indicated by axis, or the last one if axis is not specified. If n is even, the length of the transformed axis is `(n/2)+1`. If n is odd, the length is `(n+1)/2`.

Raises
IndexError

If axis is larger than the last axis of a.

`irfft`

The inverse of `rfft`.

`fft`

The 1-D FFT of general (complex) input.

`fftn`

The N-D FFT.

`rfft2`

The 2-D FFT of real input.

`rfftn`

The N-D FFT of real input.

Notes

When the DFT is computed for purely real input, the output is Hermitian-symmetric, i.e., the negative frequency terms are just the complex conjugates of the corresponding positive-frequency terms, and the negative-frequency terms are therefore redundant. This function does not compute the negative frequency terms, and the length of the transformed axis of the output is therefore `n//2 + 1`.

When `X = rfft(x)` and fs is the sampling frequency, `X` contains the zero-frequency term 0*fs, which is real due to Hermitian symmetry.

If n is even, `A[-1]` contains the term representing both positive and negative Nyquist frequency (+fs/2 and -fs/2), and must also be purely real. If n is odd, there is no term at fs/2; `A[-1]` contains the largest positive frequency (fs/2*(n-1)/n), and is complex in the general case.

If the input a contains an imaginary part, it is silently discarded.

Examples

```>>> import scipy.fft
>>> scipy.fft.fft([0, 1, 0, 0])
array([ 1.+0.j,  0.-1.j, -1.+0.j,  0.+1.j]) # may vary
>>> scipy.fft.rfft([0, 1, 0, 0])
array([ 1.+0.j,  0.-1.j, -1.+0.j]) # may vary
```

Notice how the final element of the `fft` output is the complex conjugate of the second element, for real input. For `rfft`, this symmetry is exploited to compute only the non-negative frequency terms.