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: | ;Usage: | ||
:{| class="einrahmen" | |||
|- | |||
|<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 | ||
;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: [[ | ;See also: [[../npow2|npow2]], [[../exp|exp]], [[../log2lin|lin2log, log2lin]] | ||
;Note: For the inverse function the [[ | ;Note: For the inverse function use the [[../#Operators|operater ''^'']] or the function [[../exp|exp]]; e.g.: 10^''x'', e^''x'', ... | ||
[[../#Functions|<function list>]] | |||
Example: | Example: | ||
<pre> | <pre> | ||
#a := eval | #a := eval 20*log(2) // convert factor 2 to 6dB | ||
#b := eval | #b := eval 20*log(2,10) // same as above | ||
#c := eval | #c := eval 20*log(vv(2,10,20,50,100)) | ||
// | // $#c = { 6.02, 20, 26.02, 33.98, 40 } | ||
</pre> | </pre> | ||
Latest revision as of 12:13, 21 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 use the operater ^ or the function exp; e.g.: 10^x, e^x, ...
Example:
#a := eval 20*log(2) // convert factor 2 to 6dB
#b := eval 20*log(2,10) // same as above
#c := eval 20*log(vv(2,10,20,50,100))
// $#c = { 6.02, 20, 26.02, 33.98, 40 }
