Programmer Guide/SPU Reference/LOG: Difference between revisions

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{{DISPLAYTITLE:{{SUBPAGENAME}}}}
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====LOG====
Compute logarithm of <var>A</var> to the base <var>B</var>.
 
==<code>[SPU LOG <var>A B</var> OUT <var>Y</var>]</code>==
=====Usage:=====
{|class="einrahmen"
 
!In !!Out !!Description
<code>LOG <var>a b</var></code>
 
=====Inputs:=====
 
{|
|-
|-
|a
|<var>A<sub>number</sub></var>, <var>B<sub>number</sub></var>
|number or vector
|<var>Y<sub>number</sub></var>
|<var>Y</var> = log<sub><var>B</var></sub>(<var>A</var>)
|-
|-
|b
|<var>A<sub>vector</sub></var>, <var>B<sub>number</sub></var>
|number or vector
|<var>Y<sub>vector</sub></var>
|}
|<var>Y</var>[i] = log<sub><var>B</var></sub>(<var>A</var>[i])
 
=====Outputs:=====
 
{|
|-
|-
|<var>y</var>
|<var>A<sub>vector</sub></var>, <var>B<sub>vector</sub></var>  
|number or vector (same type as a)
|<var>Y<sub>vector</sub></var>
|<var>Y</var>[i] = log<sub><var>B</var>[i]</sub>(<var>A</var>[i])
|}
|}
with: 0 &le; i &lt; length of <var>A<sub>vector</sub></var>


=====Function:=====
note:  
 
:The logarithm is computed using the following formula: <code>y = ln(a)/ln(b)</code>.
Compute logarithm of <var>a</var> to base <var>b</var>.
:<code>ln</code> is the natural logarithm and both <code>a</code> and <code>b</code> must be greater than zero
 
;See also:
if <var>a</var> and <var>b</var> are numbers: <var>y</var> = log<var>b</var>(<var>a</var>)
<[[../#Signal Processing Atoms|SP-atoms]]>
 
<!-- AN, 2.5.2011 -->
if <var>a</var> is a vector and <var>b</var> a number: <var>y</var>[i] = log<var>b</var>(<var>a</var>[i])
 
if <var>a</var> and <var>b</var> are vectors: <var>y</var>[i] = log<var>b</var>[i](<var>a</var>[i])
 
Both <var>a</var>|<var>a</var>[i] and <var>b</var>|<var>b</var>[i] must be greater than zero (otherwise the result is set to 0). If <var>a</var>|<var>a</var>[i] is smaller than the smallest number representable in single precision, the logarithm is set to the exponent of this number.

Latest revision as of 12:39, 2 May 2011

Compute logarithm of A to the base B.

[SPU LOG A B OUT Y]

In Out Description
Anumber, Bnumber Ynumber Y = logB(A)
Avector, Bnumber Yvector Y[i] = logB(A[i])
Avector, Bvector Yvector Y[i] = logB[i](A[i])

with: 0 ≤ i < length of Avector

note:

The logarithm is computed using the following formula: y = ln(a)/ln(b).
ln is the natural logarithm and both a and b must be greater than zero
See also

<SP-atoms>

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