# windowhighpass¶

windowhighpass

Increases spatial frequency within a specified square neighbourhood

Result = windowhighpass(expression, windowlength)

expression

spatial scalar

windowlength

spatial, non spatial scalar

Result

spatial scalar

## Options¶

--unittrue or --unitcell

--unittrue

windowlength is measured in true length (default)

--unitcell

windowlength is measured in number of cell lengths

## Operation¶

For each cell c its windowhighpass value is computed as follows. A square window with the cell c in its centre is defined by windowlength. The windowlength is the length of the window in horizontal and vertical directions. For each cell i which is entirely or partly in the window and which is not the centre cell c the fraction of the cell in the window is determined. This is the area of the part of the cell in the window divided by the total area of a cell. Let fraction(i) be this fraction; let expression(i) be the expression value of a surrounding cell i and expression(c) the expression value of the centre cell c. The windowhighpass filter value on the centre cell c is calculated according to:

$windowhighpass(c) = 2 * expression(c) * { \sum^n_{i=1} fraction(i) } - { \sum^n_{i=1} ( fraction(i) * expression(i) ) }$

where n is the number of cells i surrounding the centre cell C in the window. This computation is performed for all cells: for each cell the highpass(C) value is assigned to the corresponding cell on Result.

## Notes¶

The cell value on windowlength should be greater than 0, else a missing value is assigned to the corresponding cell on Result.

A cell on windowlength with a missing value results in a missing value on Result at the corresponding cell. However, if a missing value on windowlength occurs in a cell which is not the centre cell of the window the expression value in that cell is included in the computation of the highpass value in the window.

## Group¶

This operation belongs to the group of Neigbourhood operators; window operators

## Examples¶

1. • pcrcalc
binding
Result2 = Result2.map;
Expr = Expr.map;
WinLen2 = WinLen2.map;
initial
report Result2 = windowhighpass( Expr, WinLen2);

• python
Result2 = windowhighpass( Expr, WinLen2)
 Result2.map Expr.map WinLen2.map

2. • pcrcalc
binding
Result1 = Result1.map;
Expr = Expr.map;
initial
report Result1 = windowhighpass( Expr, 6);

• python