# $ZLN

Returns the natural logarithm of the specified number.

## Synopsis

$ZLN(n)

### Parameter

Argument | Description |
---|---|

n | Any positive nonzero number, which can be specified as a value, a variable, or an expression. |

## Description

$ZLN returns the natural logarithm (base e) value of n.

Specifying zero or a negative number results in an <ILLEGAL VALUE> error.

The corresponding natural logarithm power function is $ZEXP.

## Examples

The following example writes the natural log of the integers 1 through 10:

FOR x=1:1:10 { WRITE !,"The natural log of ",x," = ",$ZLN(x) } QUIT

Copy code to clipboard

returns:

The natural log of 1 = 0 The natural log of 2 = .6931471805599453089 The natural log of 3 = 1.098612288668109691 The natural log of 4 = 1.386294361119890618 The natural log of 5 = 1.609437912434100375 The natural log of 6 = 1.791759469228055002 The natural log of 7 = 1.945910149055313306 The natural log of 8 = 2.079441541679835929 The natural log of 9 = 2.197224577336219384 The natural log of 10 = 2.302585092994045684

Copy code to clipboard

The following example shows the relationship between $ZLN and $ZEXP:

SET x=$ZEXP(1) ; x = 2.718281828459045236 WRITE $ZLN(x)

Copy code to clipboard

returns 1.

WRITE $ZLN(0)

Copy code to clipboard

issues an <ILLEGAL VALUE> error.