Map and Table Calculation

Assigning undefined values

To assign the undefined value to a pixel in an output map or to a record in an output column that uses a value domain, use the question mark ?.

To assign the undefined value to a pixel in an output map or to a record in an output column that uses a class, ID, string or group domain, use a question mark between double quotes "?".

Examples

MapCalc examples:

OutMap = IFF(ValueMap >= 20, ?, ValueMap)

ValueMap

OutMap

5	10	-10
20	0	30
?	40	45

5	10	-10
?	0	?
?	?	?

If a pixel in map ValueMap has a value larger than or equal to 20, then undefined is assigned to this pixel in map OutMap; else the pixel will get the original value.

OutMap = IFF(Landuse="Forest","?", Landuse)

Landuse

OutMap

Forest	Forest	Grass
Lake	Lake	Grass
?	Grass	Forest

?	?	Grass
Lake	Lake	Grass
?	Grass	?

If a pixel in map Landuse has class name "Forest", then undefined is assigned to this pixel in map Outmap; else the original class name is assigned.

TabCalc examples:

OutCol = IFF(ValueCol >= 20, ?, ValueCol)

ValueCol	OutCol
5	5
10	10
-10	-10
20	?
0	0
30	?
?	?
40	?
45	?

If a record in column ValueCol has a value larger than or equal to 20, then undefined is assigned to this record in column OutCol; else the record will get the original value.

OutCol = IFF(Landuse="Forest", "?", Landuse)

Landuse	OutCol
Forest	?
Forest	?
Grass	Grass
Lake	Lake
Lake	Lake
Grass	Grass
?	?
Grass	Grass
Forest	?

If a record in column Landuse has class name "Forest", then undefined is assigned to this record in column OutCol; else the original class name is assigned.