Description Usage Arguments Details Value Note Examples

calculate the centre of mass of the local spectra in hexagonal geometry

1 |

`dt` |
a |

`mask` |
a |

Each of the `J x 6`

spectral values is assigned a coordinate in 3D space with `x(d,j)=cos(60*(d-1))`

, `y(d,j)=sin(60*(d-1))`

, `z(d,j)=j`

, where `j`

denotes the scale and `d`

the direction. Then the centre of mass in this space is calculated, the spectral values being the masses at each vertex. The x- and y-cooridnate are then transformed into a radius `rho=sqrt(x^2+y^2)`

and an angle `phi=15+0.5*atan2(y,x)`

. `rho`

measures the degree of anisotropy at each pixel, `phi`

the orientation of edges in the image, and the third coordinate, `z`

, the central scale. If a `mask`

is provided, values where `mask==TRUE`

are set to `NA`

.

a `nx x ny x 3`

array where the third dimension denotes degree of anisotropy, angle and central scale, respectively.

Since the centre of mass is not defined for negative mass, any values below zero are removed at this point.

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