# GfsOutputSpectra

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- | [[GfsOutputSpectra]] is a [[GfsOutput]] object that allows you to obtain the Fast Fourier Transform of a given variable. The syntax is as follows: | + | [[GfsOutputSpectra]] outputs the Fast Fourier Transform of a given variable. The syntax is as follows: |

- | [ [[GfsOutput]] ] NAME { x = x_c y = y_c z = z_c Lx = L_x Ly = L_y Lz = L_z } LEVEL | + | [ [[GfsOutput]] ] NAME { |

+ | x = XC y = YC z = ZC | ||

+ | Lx = LX Ly = LY Lz = LZ | ||

+ | } LEVEL | ||

where | where | ||

- | ; NAME : is the variable used to apply the fft. | + | ; NAME : is the variable on which to apply the FFT. |

- | ; (x_c, y_c, z_c) : is the center of the line (in 1D), square (in 2D) or cube (in 3D) where the fft is applied | + | ; (XC, YC, ZC) : is the center of the line (in 1D), square (in 2D) or cube (in 3D) where the FFT is applied. |

- | ; (L_x, L_y, L_z) : is the length of the line (in 1D fft), square (in 2D fft) or cube (in 3D). | + | ; (LX, LY, LZ) : is the length of the line (for 1D FFT), square (for 2D FFT) or cube (for 3D FFT). |

- | ; LEVEL : is an optional argument that specifies the number of points in the domain where the fft is applied (2^LEVEL points in L). By default is set to the maximum level of refinement in the domain. | + | ; LEVEL : is an optional argument that specifies the number of points in the domain where the FFT is applied (2^LEVEL points in L). By default this is set to the maximum level of refinement in the domain. |

- | Note that by default the lengths is set to zero. This feature allows to perform any type of fft in 2D and 3D simulations. | + | Note that by default all the lengths are set to zero, and that at least one length must be set (to perform a 1D FFT). |

## Revision as of 21:07, 2 October 2011

**GfsOutputSpectra** outputs the Fast Fourier Transform of a given variable. The syntax is as follows:

[ GfsOutput ] NAME { x = XC y = YC z = ZC Lx = LX Ly = LY Lz = LZ } LEVEL

where

- NAME
- is the variable on which to apply the FFT.
- (XC, YC, ZC)
- is the center of the line (in 1D), square (in 2D) or cube (in 3D) where the FFT is applied.
- (LX, LY, LZ)
- is the length of the line (for 1D FFT), square (for 2D FFT) or cube (for 3D FFT).
- LEVEL
- is an optional argument that specifies the number of points in the domain where the FFT is applied (2^LEVEL points in L). By default this is set to the maximum level of refinement in the domain.

Note that by default all the lengths are set to zero, and that at least one length must be set (to perform a 1D FFT).