FT for Ruby¶ ↑

This gem contains a library written in C to perform:

• Discrete Hartley Transform (DHT),

• Fast Hartley Transform (FHT),

• Discrete Fourier Transform (DFT),

• Fast Fourier Transform (FFT).

The extension allows to do the transform in both directions. Moreover all the transforms are avaliable in one and two dimensions to process.

Instalation¶ ↑

To install the extension clone the repository on your machine:

git clone git://github.com/placek/ft.git

build a gem:

gem build ft.gemspec

and install it:

gem install ft-*.gem

Requirements¶ ↑

Data for Fourier transforms is a set of complex numbers. It need to be storaged in two seperate arrays of the same dimensions. First one will contain real parts of numbers, second one - imaginary parts. The length of data should be a power of 2 (otherwise FT methods will return nil).

Data for Hartley transforms is a set of real numbers. Here the only restriction is a length of array - it should be a multiplication of 2

Usage¶ ↑

Import the FT gem:

require 'ft'

Prepare some data to process:

data =   [[2.0, 1.0, 1.0, 2.0],   # real parts of data
          [0.0, 0.0, 0.0, 0.0]]   # imaginary parts of data

data2d = [[[1.0, 1.0, 1.0, 1.0],  # real parts
           [1.0, 2.0, 2.0, 1.0],  #
           [1.0, 2.0, 2.0, 1.0],  #
           [1.0, 1.0, 1.0, 1.0]], #
          [[0.0, 0.0, 0.0, 0.0],  # imaginary parts
           [0.0, 0.0, 0.0, 0.0],  #
           [0.0, 0.0, 0.0, 0.0],  #
           [0.0, 0.0, 0.0, 0.0]]] #

hdata =   [2.0, 1.0, 1.0, 2.0]    # data for DHT or FHT
hdata2d = [[1.0, 1.0, 1.0, 1.0],  # 2D data for DHT or FHT
           [1.0, 2.0, 2.0, 1.0],  #
           [1.0, 2.0, 2.0, 1.0],  #
           [1.0, 1.0, 1.0, 1.0]]  #

Make some data processing with FFT:

result = data.fft             # will return FFT
result.rfft                   # will return reverse FFT
result2d = data.fft2d         # will return FFT for 2D data
result2d.rfft2d               # will return reverse FFT for 2D data

And some data processing with DFT:

result = data.dft             # will return DFT
result.rdft                   # will return reverse DFT
result2d = data.dft2d         # will return DFT for 2D data
result2d.rdft2d               # will return reverse DFT for 2D data

Data processing with DHT or FHT:

result = hdata.dht
result = hdata.fht
result = hdata2d.dht2d
result = hdata2d.fht2d

Credits¶ ↑

• Paweł Placzyński

• Jude Sutton