DATAMANIP commands


PROGRAM NAME

klog - Compute Logarithm

DESCRIPTION

klog computes the logarithm of an object element by element. If the object has an associated mask, the operation will be gated so that the logarithm is computed only on valid elements, indicated by non-zero mask values. A zero mask value will cause the value of the corresponding element in the input object to be transferred the output object.

Three standard-base logarithms are provided, and alternate bases can be specified using the -base option. be returns the natural logarithm of x, and b2 and b10 return the logarithm to base 2 and 10 respectively.

The -offset option can be set to TRUE if the logarithm is to operate on the input value plus 1 (log(x+1)). This improves accuracy for very small input values.

If the argument to the log is less than or equal to zero, then a large negative number is returned (-1.0e38).

If the input object has a map, then only the map values are modified, and the vlaue data is not touched.

REQUIRED ARGUMENTS

-i
type: infile
desc: input data object
-o
type: outfile
desc: resulting output data object

Mutually Exclusive Group; you must specify ONE of:

-be
type: flag
desc: Compute logarithm using natural base 2.71828...
OR
-b10
type: flag
desc: Compute logarithm using base 10
OR
-b2
type: flag
desc: Compute logarithm using base 2
OR
-base
type: double
desc: User Specified base
default: 2
bounds: no range checking

OPTIONAL ARGUMENTS

-offset
type: boolean
desc: Operate either on value [False] or value+1 [True]
default: true

EXAMPLES

SEE ALSO

DATAMANIP::klogexp

RESTRICTIONS

REFERENCES

COPYRIGHT

Copyright (C) 1993 - 1997, Khoral Research, Inc. ("KRI") All rights reserved.