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LOG Function

Computes the logarithm of the first argument with a base of the second argument.

  • First argument can be a Decimal or Integer literal or a reference to a column containing numeric values.

  • Second argument, the base, must be an Integer value or column reference.

Wrangle vs. SQL: This function is part of Wrangle, a proprietary data transformation language. Wrangle is not SQL. For more information, see Wrangle Language.

Basic Usage

Numeric literal example:

log(49, 7)

Output: Returns 2.

Column reference example:

log(MyValue, 5)

Output: Returns the exponent that raises 5 to yield the MyValue column.

Syntax and Arguments

log(result_numeric_value, base_numeric_value)

Argument

Required?

Data Type

Description

result_numeric_value

Y

string, decimal, or integer

Name of column or Decimal or Integer literal that is generated by the LOG function

base_numeric_value

Y

string, decimal, or integer

Name of column or Decimal or Integer literal that serves as the base for computing the LOG function

For more information on syntax standards, see Language Documentation Syntax Notes.

result_numeric_value

Name of the column or numeric literal. Value must be greater than 0.

  • Missing input values generate missing results.

  • Literal numeric values should not be quoted. Quoted values are treated as strings.

  • Multiple columns and wildcards are not supported.

Usage Notes:

Required?

Data Type

Example Value

Yes

String (column reference) or Integer or Decimal literal

49

base_numeric_value

Name of the column or Integer literal that is used for the exponential calculation.

注意

This base value must be a positive integer. If this value is not specified, 10 is used as the base value.

  • Missing input values generate missing results.

  • Literal numeric values should not be quoted. Quoted values are treated as strings.

  • Multiple columns and wildcards are not supported.

Usage Notes:

Required?

Data Type

Example Value

No

String (column reference) or Integer or Decimal literal

7

Examples

提示

For additional examples, see Common Tasks.

Example - Exponential functions

This example demonstrates the exponential functions.

Functions:

Item

Description

EXP Function

Computes the value of e raised to the specified power. The value can be a Decimal or Integer literal or a reference to a column containing numeric values.

LN Function

Computes the natural logarithm of an input value. The value can be a Decimal or Integer literal or a reference to a column containing numeric values.

LOG Function

Computes the logarithm of the first argument with a base of the second argument.

POW Function

Computes the value of the first argument raised to the value of the second argument.

Source:

rowNum

X

1

-2

2

1

3

0

4

1

5

2

6

3

7

4

8

5

Transformation:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

EXP (X)

Parameter: New column name

'expX'

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

LN (expX)

Parameter: New column name

'ln_expX'

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

LOG (X)

Parameter: New column name

'logX'

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

POW (10,logX)

Parameter: New column name

'pow_logX'

Results:

In the following, (null value) indicates that a null value is generated for the computation.

rowNum

X

expX

ln_expX

logX

pow_logX

1

-2

0.1353352832366127

-2

(null value)

(null value)

2

-1

0.1353352832366127

-0.9999999999999998

(null value)

(null value)

3

0

1

0

(null value)

0

4

1

2.718281828459045

1

0

1

5

2

7.3890560989306495

2

0.30102999566398114

1.9999999999999998

6

3

20.085536923187668

3

0.47712125471966244

3

7

4

54.59815003314423

4

0.6020599913279623

3.999999999999999

8

5

148.41315910257657

5

0.6989700043360187

4.999999999999999