Map and Table Calculation

EXP( ) function

Returns the base of the natural logarithm e raised to a power a, i.e. ea.

Syntax

EXP(Value)

Input

Value is the exponent to which e is raised
Domain type: any Value domain

Output

EXP returns: a real value
Domain: system domain Value
Value range: >0

Notes:

Tips:

Usable in

MapCalc, TabCalc, Simple calculators

Examples

Pocket line calculator examples:

? EXP(1)

returns 2.7183

? EXP(SQ(2))

returns 54.5982

MapCalc example:

OutMap = EXP(InMap)

 

InMap

OutMap

2.0 1.0 0.5
0.2 0.0 -1.0
? -0.4 -0.1
7.3891 2.7183 1.6487
1.2214 1.0000 0.3679
? 0.6703 0.9048

TabCalc example:

OutCol = EXP(InCol)

 

InCol

OutCol

2.0

7.3891

1.0

2.7183

0.5

1.6487

0.2

1.2214

0.0

1.0000

-1.0

0.3679

?

?

-0.4

0.6703

-0.1

0.9048

Applied example: exponential growth functions

In general, an exponential growth function is defined as:

An = A0 * eperc/100*n

where:

An

is the amount after n years

A0

is the amount in year 0

perc

is the growth rate as a percentage per year

n

is the number of years

 

In ILWIS this function looks like:

An = A0 * EXP(perc/100*n)

The expected total residential area after 4 years, of a residential area of 1136 ha with an estimated growth rate of 6% per year, is:

1136 * EXP(6/100*4) = 1444

For the other landuse areas the results are:

 

LandUse

AreaHaY0

GrowPerc

AreaHaY4

Residential

1136

6

1444

Commercial

116

2

126

Industrial

173

3

195

Institutional

137

1

143

Recreational

77

2

83

Transportation

18

1

19

 

Where:

Column AreaHaY0 contains the areas in hectares for each land use class in year 0.

Column GrowPerc contains growth rates per year.

Column AreaHaY4 contains the areas of the land use classes after 4 years.

Notes:

See also: