Map and Table Calculation

POW( ) function

Returns the result of a value a raised to a power b, i.e. a^b. 

Syntax

POW(Value a, Value b)

Input

Output

Notes:

• The POW(a,b) function is equivalent to a^b where ^ is the exponential operator.
• When the base value is negative, the exponent has to be a whole integer value (otherwise the output will be undefined).
• When one of the input parameters is undefined, or when both input parameters are undefined, the output will also be undefined.

Tips:

• Using the function in the form of POW(a, 1/n) returns the n^th root a (ⁿÖa). See also laws of exponents.
• When the definition symbol = is used, a dependent output map or dependent output column is created; when the assignment symbol := is used, the dependency link is immediately broken after the output map/column has been calculated.

Usable in

MapCalc, TabCalc, Simple calculators

Examples

Pocket line calculator examples:

MapCalc example:

OutMap = POW(InMap,3)

TabCalc example:

OutCol = POW(InColA,InColB)

Applied example: exponential growth functions

In general, an exponential growth function is defined as:

A_n = A₀ * (1 + perc/100)ⁿ

where:

In ILWIS this function looks like:

An = A0 * POW(1 + 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 * POW(1 + 6/100, 4) = 1434

For the other landuse areas the results are:

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:a

• Instead of years you may also calculate in months, days, etc.
• For an example of another growth function, see the EXP function.

See also: