if then else

if then else

Boolean condition determining whether value of the first or second expression is assigned to result

# Python
Result = ifthenelse(condition, expression1, expression2)

# PCRcalc
Result = if(condition then expression1 else expression2)
Result = if(condition, expression1, expression2)

expression1

spatial, non spatial boolean, nominal, ordinal, scalar, directional, ldd

condition

spatial, non spatial boolean

expression2

spatial, non spatial type of expression1

Result

spatial; non spatial if condition, expression1 and expression2 are all non spatial type of expression1

Operation

The cell values on condition are interpreted as Boolean values where 1 is TRUE and 0 is FALSE. For each cell, the cell value on condition determines whether the value of the corresponding cell on expression1 or expression2 is assigned to the corresponding cell on Result: if condition has a cell value 1 (TRUE) the value on expression1 is assigned Result, if condition has a cell value 0 (FALSE) the value on expression2 is assigned to Result.

Notes

A cell with a missing value on condition results in a missing value on Result at the corresponding cell. A cell with a value 1 (TRUE) on condition and a missing value on expression1 results in a missing value on Result. Also, a cell with a value 0 (FALSE) on condition and a missing value on expression2 results in a missing value on Result.

Remember that the data type of expression1 must correspond with the data type of expression2.

Comma’s between condition, expression1 and expression2 in the command line is an alternative notation for then else.

If you want to cut an local drain direction map (data type ldd), use the operator lddmask instead of if then else. The operator if then else allows for cutting expressions (expression1, expression2) of data type ldd but we advice to use it in very special cases only; it will result in an unsound ldd.

Group

This operation belongs to the group of Conditional operators

See Also

if then (else) pitfalls, cover, defined, lddmask

Examples

1. • pcrcalc

   binding

   Result = Result.map;

   Cond = Cond.map;

   Expr1 = Expr1.map;

   Expr2 = Expr2.map;

   initial

   report Result = if(Cond,Expr1,Expr2);

   
   

   • python

   Cond = readmap(“Cond.map”)

   Expr1 = readmap(“Expr1.map”)

   Expr2 = readmap(“Expr2.map”)

   Result = ifthenelse(Cond, Expr1, Expr2)

   Result.map	Cond.map	Expr1.map	Expr2.map