windowhighpass

Increases spatial frequency within a specified square neighbourhood

```
Result = windowhighpass(expression, windowlength)
```

- expression
- spatial scalar
- windowlength
- spatial, non spatial scalar
- Result
- spatial scalar

`--unittrue` or `--unitcell`

`--unittrue`- windowlength is measured in true length (default)
`--unitcell`- windowlength is measured in number of cell lengths

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.

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.

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

- • pcrcalcbindingResult2 = Result2.map;Expr = Expr.map;WinLen2 = WinLen2.map;initialreport Result2 = windowhighpass( Expr, WinLen2);• pythonExpr = readmap(“Expr.map”)WinLen2 = readmap(“WinLen2.map”)Result2 = windowhighpass( Expr, WinLen2)
Result2.map Expr.map WinLen2.map - • pcrcalcbindingResult1 = Result1.map;Expr = Expr.map;initialreport Result1 = windowhighpass( Expr, 6);• pythonExpr = readmap(“Expr.map”)Result1 = windowhighpass( Expr, 6)
Result1.map Expr.map