Programmer Guide/Command Reference/EVAL/log: Difference between revisions
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{{DISPLAYTITLE:log, ln, ld}} | {{DISPLAYTITLE:log, ln, ld}} | ||
Compute the logarithm of the argument ''x'' element by element. | Compute the logarithm of the argument ''x'' element by element. | ||
;Usage: '''<code>log(<var>x</var> , <var>b</var></code>''' | ;Usage: | ||
:{| frame="0" | |||
|'''<code>log(<var>x</var> , <var>b</var></code>''' ||:general logarithm to base ''b'' | |||
|'''<code>log(<var>x</var>)</code>''' ||:common logarithm (base 10) | |||
|'''<code>ln(<var>x</var>)</code>''' ||: natural logarithm (base e) ||: alias: <code>log(''x'','''e''')</code> | |||
|'''<code>ld(<var>x</var>)</code>''' ||: logarithm to the base 2 ||: alias: <code>log(''x'','''2''')</code> | |||
|} | |||
:;<var>x</var>: a scalar, vector or matrix; all elements must be greater than 0 | :;<var>x</var>: a scalar, vector or matrix; all elements must be greater than 0 | ||
:;<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 | ||
Revision as of 13:33, 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
- 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
