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`orientation, `

`data`, `widths` [, `orientation`,
`values`, `wavenumbers`, `grid`, `aspect`, `order`,
/vocal, /getj]

Determines local orientation in 2D or 3D data employing a method based on local Fourier Transforms.

`data`The 2D or 3D array in which orientations are to be determined.

`widths`must be a 2 or 3-element vector containing the FWHM of the Gaussian smoothing kernels applied in the dimensions (0 means no smoothing).

`grid`is a 2 or 3-element vector containing the desired dimensions of the results. If it is not specified, then the results will have the same dimensions as

.`data``aspect`specifies the dimensions of a pixel, if they do not have an aspect ratio of 1.

`order`contains the approximation order of the calculations, a number between 1 and 4 (default, most accurate).

`orientation`The found orientation is returned in this argument (if specified), unless

`/getj`

is specified. The orientation is expressed in the 2d case as an angle in radians measured counterclockwise from the positive x-axis, and in the 3D case as a 2-element vector containing the x and y coordinates of the orientation vector relative to a unit z coordinate.`values`The found eigenvalues (measures for the data gradients in the principal directions) are returned in this argument (if specified), unless

`/getj`

is specified. The eigenvalues are returned in descending order.`wavenumber`-
By default, the determined local wavenumber in the direction of the found orientation is returned in this argument (if specified), unless

`/getj`

is specified. If`/perpendicular`

is specified, then – for two-dimensional data only – the local wavenumber in the direction perpendicular to the found orientation is returned instead. The wavenumber is measured in units of one data element. A data set with values equal to sin(x) returns a wavenumber of 1 for the perpendicular wavenumber, and 0 for the parallel wavenumber. If a random data set is smoothed over FWHM

in one direction, then the parallel local wavenumber is on average equal to about 1.65/`w`

.`w`

`/getj`

If specified, then the unique elements of the inertia tensor are returned in

(the diagonal elements) and`values`

(the off-diagonal elements), and the local power in`orientation`

. This keyword is supplied for debugging purposes and may be withdrawn in the future.`wavenumber``/vocal`

Induces periodical display of the progress status.

The returned orientations are ambiguous over 180 degrees.

• orientation details: |

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