# unu-fft - Man Page

Fast Fourier Transform of selected axes

## Synopsis

**unu fft** <*dir*> **-a**,**--axes** <*ax0* ...> [**-pr**,**--planrigor** <*pr*>] [**-r**,**--rescale** <*bool*>] [**-w**,**--wisdom** <*filename*>] [**-i**,**--input** <*nin*>] [**-ri**,**--realinput**] [**-o**,**--output** <*nout*>]

## Description

Fast Fourier Transform of selected axes. Initial attempt at wrapping the FFTW3 library; options are likely to change in Teem 2.0.

- Uses
**nrrdFFT**

## Options

- <
*dir*> forward (“

**forw**”, “**f**”) or backward/inverse ("back", "b") (“**back**”, “**b**”) transform- -a <
*ax0*...> , --axes <*ax0*...> the one or more axes that should be transformed (1 or more

*unsigned int*s)- -pr <
*pr*> , --planrigor <*pr*> rigor with which fftw plan is constructed. Options include:

- “
**e**”, “**est**”, “**estimate**”: only an estimate - “
**m**”, “**meas**”, “**measure**”: standard amount of measurements of system properties - “
**p**”, “**pat**”, “**patient**”: slower, more measurements - “
**x**”, “**ex**”, “**exhaustive**”: slowest, most measurements

default: “

**est**”- “
- -r <
*bool*> , --rescale <*bool*> scale fftw output (by sqrt(1/N)) so that forward and backward transforms will get back to original values (

*bool*); default: “**true**”- -w <
*filename*> , --wisdom <*filename*> A filename here is used to read in fftw wisdom (if the file exists already), and is used to save out updated wisdom after the transform. By default (not using this option), no wisdom is read or saved.

*Note*: no wisdom is gained (that is, learned by FFTW) with planning rigor “**estimate**”. (*string*)- -i <
*nin*> , --input <*nin*> input

*nrrd*- -ri , --realinput
input is real-valued, so insert new length-2 axis

**0**and set complex component to**0.0**. Axes to transform (indicated by “**-a**” will be incremented accordingly.- -o <
*nout*> , --output <*nout*> output

*nrrd*(*string*); default: “**-**”