2.2.23. averageDown

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Purpose

Average each data block of size 'packing' into single values thus reducing the former grid to grid/packing.

Usage

	> averageDown options ASCII table(s) 
	

Options

-c / --coordinates [ pos ]

column label of coordinates

-p / =--packing=[ 2 2 2 ]

size of packed group

=--shift=[ 0 0 0 ]

shift vector of packing stencil

-g / --grid

grid in x,y,z (optional)

-s / --size

size in x,y,z (optional)

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Details

For a periodic and regular grid stored in an ASCII table with x as fastest and z as slowest varying coordinate, calculate the average per block of given size. Grid resolution is reduced by the factor resulting from the chosen size of the packing stencil.

Figure 1 illustrates the concept in two dimensions with a 2 by 2 packing stencil. The original 4 by 4 grid is shown in light gray and might result from a 2 by 2 finite element mesh (black lines) with linear interpolation functions, thus containing four integration points each. During averaging, the stencil is moved across the whole grid in steps of 2 grid points along x and 2 grid points along y, i.e., in a non-overlapping fashion.

The (black) points of the resulting 4/2 by 4/2 = 2 by 2 grid fall into the center of the finite elements since a stencil shift of (0, 0) was employed in this example.

Using a stencil shift of either (-1,-1), (-1,1), (1,1), or (1,-1) in the example of Figure 1 would result in the new grid coinciding with the nodes of the finite elements and averaged from their four neighboring integration points (light gray; periodicity of the original data is always implied).