Programmer Guide/Command Reference/EVAL/log2lin: Difference between revisions
From STX Wiki
< Programmer Guide | Command Reference | EVAL
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 6: | Line 6: | ||
:;<var>ref</var>: the reference value; must be a positive number (default=1) | :;<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) | :;<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'' | ;Result: The result ''r'' has the same type as ''x'' and contains the converted elements of ''x''. | ||
::*lin2log: ''r''<sub>i,j</sub> = fac * log<sub>10</sub>(''x''<sub>i,j</sub> / ''ref'') | ::*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'') | ::*log2lin: ''r''<sub>i,j</sub> = ''ref'' * 10 ^ (''x''<sub>i,j</sub> / ''fac'') | ||
;See also: [[Programmer_Guide/Command_Reference/EVAL/npow2|log]], [[Programmer_Guide/Command_Reference/EVAL/exp|exp]] | ;See also: [[Programmer_Guide/Command_Reference/EVAL/npow2|log]], [[Programmer_Guide/Command_Reference/EVAL/exp|exp]] | ||
| Line 14: | Line 14: | ||
Example: | Example: | ||
<pre> | <pre> | ||
#a := | // #spe is a vector containing a complex spectrum | ||
#aref := set '20e-6' // reference value: 20 micro Pascal | |||
# | #logamp := eval lin2log(cr2len($#spe), $#aref) // the log. amplitude spectrum in dB | ||
// | |||
</pre> | </pre> | ||
[[Programmer_Guide/Command_Reference/EVAL#Functions|<function list>]] | [[Programmer_Guide/Command_Reference/EVAL#Functions|<function list>]] | ||
Revision as of 15:37, 6 April 2011
Convert the elements of x to logarithmic values (e.g. dB) and vice versa.
- Usage
lin2log(x {, ref {, fac}})log2lin(x {, ref {, fac}})- x
- a scalar, vector or matrix
- ref
- the reference value; must be a positive number (default=1)
- fac
- the factor; must be a positive number (default=20)
- Result
- The result r has the same type as x and contains the converted elements of x.
- lin2log: ri,j = fac * log10(xi,j / ref)
- log2lin: ri,j = ref * 10 ^ (xi,j / fac)
Example:
// #spe is a vector containing a complex spectrum #aref := set '20e-6' // reference value: 20 micro Pascal #logamp := eval lin2log(cr2len($#spe), $#aref) // the log. amplitude spectrum in dB
