Programmer Guide/Command Reference/EVAL/log: Difference between revisions
From STX Wiki
< Programmer Guide | Command Reference | EVAL
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 5: | Line 5: | ||
:'''<code>ln(<var>x</var>)</code>''' ... natural logarithm (base e); alias: <code>log(''x'','''e''')</code> | :'''<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> | :'''<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: [[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]] | ||
Revision as of 13:30, 6 April 2011
Compute the logarithm of the argument x element by element.
- Usage
log(x , blog(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
