Difference between revisions of "LOG"

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The '''LOG''' math function returns the natural logarithm of a specified numerical value.
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The [[LOG]] math function returns the natural logarithm of a specified numerical value.
  
  
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{{PageSyntax}}
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: {{Parameter|logarithm!}} = [[LOG]]({{Parameter|value}})
  
''Syntax:'' logarithm = LOG(value)
 
  
 
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{{PageDescription}}
 
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* {{Parameter|value}} MUST be greater than 0. [[ERROR Codes|"Illegal function call" error]] occurs if negative or zero values are used.
* Value parameter MUST be greater than 0!
 
 
* The natural logarithm is the logarithm to the base '''e = 2.718282''' (approximately).
 
* The natural logarithm is the logarithm to the base '''e = 2.718282''' (approximately).
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* The natural logarithm of ''a'' is defined as the integral from 1 to ''a'' of dx/x.
 
* Returns are default [[SINGLE]] precision unless the value parameter uses [[DOUBLE]] precision.
 
* Returns are default [[SINGLE]] precision unless the value parameter uses [[DOUBLE]] precision.
  
  
''Example:'' [[FUNCTION]] to find the base ten logarithm or a numerical value.
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{{PageExamples}}
 
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''Example 1:'' [[FUNCTION]] to find the base ten logarithm of a numerical value.
 
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{{CodeStart}}
:FUNCTION Log10(value)  
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FUNCTION Log10#(value AS DOUBLE) {{Cl|STATIC}}
:: Log10 = LOG(value) / LOG(10#)  
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  Log10# = LOG(value) / LOG(10.#)  
:END FUNCTION
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END FUNCTION '' ''
 
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{{CodeEnd}}
  
''Explanation:'' The natural logarithm of the value is divided by the base 10 logarithm. The LOG of ten is designated as a DOUBLE precision return by using # after the 10 value.
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:''Explanation:'' The natural logarithm of the value is divided by the base 10 logarithm. The LOG of ten is designated as a DOUBLE precision return by using # after the Log10 value. The return tells you the number of times 10 goes into a value.
  
  
''See also:'' [[EXP]]
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''Example 2:'' A binary FUNCTION to convert [[INTEGER]] values using LOG to find the number of digits the return will be.
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{{CodeStart}} '' ''
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FUNCTION BIN$ (n&)
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  IF n& < 0 THEN EXIT FUNCTION            'positive numbers only! negative error!
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  FOR p% = 0 TO INT({{Cl|LOG}}(n& + .1) / {{Cl|LOG}}(2))    ' added +.1 to get 0 to work
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    IF n& {{Cl|AND}} 2 ^ p% THEN s$ = "1" + s$ ELSE s$ = "0" + s$  'find bits on
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  NEXT p%
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  IF s$ = "" THEN BIN$ = "&B0" ELSE BIN$ = "&B" + s$      'check for zero return '' ''
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END FUNCTION
  
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{{CodeEnd}}
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: ''Explanation:'' The LOG of a '''positive''' [[INTEGER]] value is divided by the LOG of 2 to determine the number of binary digits that will be returned. The FOR loop compares the value with the exponents of two and determines if a bit is ON or OFF as "1" or "0".
  
  
==Navigation:==
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{{PageSeeAlso}}
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*[[EXP]], [[&B]] (binary number)
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*[http://qb64.net/wiki/index.php?title=Mathematical_Operations#Derived_Mathematical_Functions Derived Trigonometric Functions]
  
[[Keyword_Reference_-_Alphabetical|Go to Keyword Reference - Alphabetical]]
 
  
[[Keyword Reference - By usage|Go to Keyword Reference - By usage]]
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{{PageNavigation}}

Latest revision as of 14:40, 9 October 2017

The LOG math function returns the natural logarithm of a specified numerical value.


Syntax

logarithm! = LOG(value)


Description

  • value MUST be greater than 0. "Illegal function call" error occurs if negative or zero values are used.
  • The natural logarithm is the logarithm to the base e = 2.718282 (approximately).
  • The natural logarithm of a is defined as the integral from 1 to a of dx/x.
  • Returns are default SINGLE precision unless the value parameter uses DOUBLE precision.


Examples

Example 1: FUNCTION to find the base ten logarithm of a numerical value.

FUNCTION Log10#(value AS DOUBLE) STATIC Log10# = LOG(value) / LOG(10.#) END FUNCTION

Explanation: The natural logarithm of the value is divided by the base 10 logarithm. The LOG of ten is designated as a DOUBLE precision return by using # after the Log10 value. The return tells you the number of times 10 goes into a value.


Example 2: A binary FUNCTION to convert INTEGER values using LOG to find the number of digits the return will be.

FUNCTION BIN$ (n&) IF n& < 0 THEN EXIT FUNCTION 'positive numbers only! negative error! FOR p% = 0 TO INT(LOG(n& + .1) / LOG(2)) ' added +.1 to get 0 to work IF n& AND 2 ^ p% THEN s$ = "1" + s$ ELSE s$ = "0" + s$ 'find bits on NEXT p% IF s$ = "" THEN BIN$ = "&B0" ELSE BIN$ = "&B" + s$ 'check for zero return END FUNCTION

Explanation: The LOG of a positive INTEGER value is divided by the LOG of 2 to determine the number of binary digits that will be returned. The FOR loop compares the value with the exponents of two and determines if a bit is ON or OFF as "1" or "0".


See also



Navigation:
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Go to Keyword Reference - By usage
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