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-rw-r--r--numpy/fft/__init__.py8
1 files changed, 8 insertions, 0 deletions
diff --git a/numpy/fft/__init__.py b/numpy/fft/__init__.py
index fe95d8b17..37b3f0da6 100644
--- a/numpy/fft/__init__.py
+++ b/numpy/fft/__init__.py
@@ -118,8 +118,16 @@ The inverse DFT is defined as
It differs from the forward transform by the sign of the exponential
argument and the default normalization by :math:`1/n`.
+Type Promotion
+--------------
+
+`numpy.fft` promotes ``float32`` and ``complex64`` arrays to ``float64`` and
+``complex128`` arrays respectively. For an FFT implementation that does not
+promote input arrays, see `scipy.fftpack`.
+
Normalization
-------------
+
The default normalization has the direct transforms unscaled and the inverse
transforms are scaled by :math:`1/n`. It is possible to obtain unitary
transforms by setting the keyword argument ``norm`` to ``"ortho"`` (default is