LOG1P

Purpose:

Computes log(1 + x) for small x.

Syntax:

LOG1P(x)

x

-

A scalar, series or table.

Returns:

A scalar, series, or table.

Example:

log1p(1e-17)

 

returns 1.000000E-17.

 

log(1 + 1e-17)

 

returns 0.0.

Example:

expm1(log1p(1e-17))

 

returns 1.000000E-17.

 

exp(log(1 + 1e-17)) - 1

 

returns 0.0.

Remarks:

For real values, LOG1P is accurate for small x where 1 + x == 1 for double precision accuracy.

 

For small x, LOG1P(x) is approximately x, but LOG(1 + x) is approximately 0 for double precision accuracy.

 

See EXPM1 to compute EXP(x) - 1 for small x, the inverse of LOG1P.

See Also:

EXP

EXPM1

LOG

LOG10

LOG2

LN