Programmer Guide/Command Reference/EVAL/log: Difference between revisions
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:;<var>b</var>: the base of the logarithm; must be a positive number | :;<var>b</var>: the base of the logarithm; must be a positive number | ||
;Result: The result ''r'' has the same type as ''x'' and contains the logarithm of ''x'' to the specified base ''b'', computed element by element. | ;Result: The result ''r'' has the same type as ''x'' and contains the logarithm of ''x'' to the specified base ''b'', computed element by element. | ||
;See also: [[Programmer_Guide/Command_Reference/EVAL/npow2|npow2]], [[Programmer_Guide/Command_Reference/EVAL/exp|exp]] | ;See also: [[Programmer_Guide/Command_Reference/EVAL/npow2|npow2]], [[Programmer_Guide/Command_Reference/EVAL/exp|exp]], [[Programmer_Guide/Command_Reference/EVAL/lin2log|lin2log, log2lin]] | ||
;Note: For the inverse function the [[Programmer_Guide/Command_Reference/EVAL#Operators|operater ''^'']] can be used; e.g.: 10^''x'', e^''x'', ... | ;Note: For the inverse function the [[Programmer_Guide/Command_Reference/EVAL#Operators|operater ''^'']] can be used; e.g.: 10^''x'', e^''x'', ... | ||
Example: | Example: | ||
Revision as of 14:51, 6 April 2011
Compute the logarithm of the argument x element by element.
- Usage
log(x , b)general logarithm to base b log(x)common logarithm (base 10) ln(x)natural logarithm (base e) alias: log(x,e)ld(x)logarithm to the base 2 alias: log(x,2)
- x
- a scalar, vector or matrix; all elements must be greater than 0
- b
- the base of the logarithm; must be a positive number
- Result
- The result r has the same type as x and contains the logarithm of x to the specified base b, computed element by element.
- See also
- npow2, exp, lin2log, log2lin
- Note
- For the inverse function the operater ^ can be used; e.g.: 10^x, e^x, ...
Example:
#a := eval vv(1,2,3,4,5) #b := eval init(5,2,0) #c := eval vmcol($#a, $#b, $#a) // -> $#c is a matrix with 4 rows and 5 columns: // $#c[*,*] = $#a, #c[1,*] = $#b[*,0], $#c[2,*] = $#b[*,1], $#c[3,*] = $#a
