# downstream¶

downstream

Cell gets value of the neighbouring downstream cell

Result = downstream(ldd, expression)

expression
spatial boolean, nominal, ordinal, scalar, directional, ldd
ldd
spatial ldd
Result
spatial type of expression

## Operation¶

For each cell, assigns to Result the expression value of the neighbouring downstream cell, where downstream cells are determined using the local drain directions on ldd. In case a cell doesn’t have a downstream cell (i.e. a pit) its own expression value is assigned to Result.

## Notes¶

A cell with a missing value on ldd and/or expression is assigned a missing value on Result. Its upstream neighbours are assigned a missing value also.

## Group¶

This operation belongs to the group of Neighbourhood operators; local drain directions

## Examples¶

1. • pcrcalc
binding
Result = Result.map;
Ldd = Ldd.map;
Expr = Expr.map;
initial
report Result = downstream( Ldd, Expr);

• python