Programmer Guide/Command Reference/EVAL/log2lin: Difference between revisions
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{{DISPLAYTITLE:{{ | {{DISPLAYTITLE:lin2log , log2lin (alias: dB)}} | ||
==== | Convert the elements of ''x'' to logarithmic values (e.g. dB) and vice versa. | ||
;Usage: <code>lin2log(<var>x</var> {, <var>ref</var> {, <var>fac</var>}})</code> | |||
:<code>log2lin(<var>x</var> {, <var>ref</var> {, <var>fac</var>}})</code> | |||
:;<var>x</var>: a scalar, vector or matrix | |||
:;<var>ref</var>: the reference value; must be a positive number (default=1) | |||
:;<var>fac</var>: the factor; must be a positive number (default=20) | |||
;Result: The result ''r'' has the same type as ''x'' and contains the converted elements of ''x''. The following conversion algorithms are used: | |||
::*'''lin2log''': ''r''<sub>i,j</sub> = ''fac'' * log<sub>10</sub>(''x''<sub>i,j</sub> / ''ref'') | |||
::*'''log2lin''': ''r''<sub>i,j</sub> = ''ref'' * 10 ^ (''x''<sub>i,j</sub> / ''fac'') | |||
:Note: The function '''dB''' is an alias for '''log2lin''' and is implemented for compatibility with the expressions used in the [[Programmer_Guide/Command_Reference/NUM|NUM]] and [[Programmer_Guide/Command_Reference/INT|INT]] command. | |||
;See also: [[../log|log]], [[../exp|exp]], [[../fft|fft]], [[../complex arithmetic|complex arithmetic (cr2p, cp2r, cr2len)]] | |||
[[../#Functions|<function list>]] | |||
= | Example: | ||
<pre> | |||
// #spe is a vector containing a complex spectrum | |||
#aref := set '20e-6' // reference value: 20 micro Pascal | |||
#logamp := eval lin2log(cr2len($#spe), $#aref) // the log. amplitude spectrum in dB | |||
// apply 6dB attenuation to the signal stored in the vector #sig | |||
$#sig := eval $#sig * db(6) | |||
: | </pre> | ||
Latest revision as of 11:16, 21 April 2011
Convert the elements of x to logarithmic values (e.g. dB) and vice versa.
- Usage
lin2log(x {, ref {, fac}})log2lin(x {, ref {, fac}})- x
- a scalar, vector or matrix
- ref
- the reference value; must be a positive number (default=1)
- fac
- the factor; must be a positive number (default=20)
- Result
- The result r has the same type as x and contains the converted elements of x. The following conversion algorithms are used:
- lin2log: ri,j = fac * log10(xi,j / ref)
- log2lin: ri,j = ref * 10 ^ (xi,j / fac)
- Note: The function dB is an alias for log2lin and is implemented for compatibility with the expressions used in the NUM and INT command.
- See also
- log, exp, fft, complex arithmetic (cr2p, cp2r, cr2len)
Example:
// #spe is a vector containing a complex spectrum #aref := set '20e-6' // reference value: 20 micro Pascal #logamp := eval lin2log(cr2len($#spe), $#aref) // the log. amplitude spectrum in dB // apply 6dB attenuation to the signal stored in the vector #sig $#sig := eval $#sig * db(6)
