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Author Topic: Can anyone help with logs.  (Read 1921 times)

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Offline Tempeboy

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Can anyone help with logs.
« on: June 09, 2007, 02:18:47 AM »
I am trying to work out logorithms.  I understand the concept a little, but am hoping some of our more gifted brothers and sisters could offer some wisdom in everyday language.  I understand that it is a way to communicate large numbers, but as to how etc I get lost.

cheers

TB. ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ???
Roughly roundabout somewhere in the eighteenth or nineteenth century, Sodomite begat Homosexual out of moral, medical and legal models, bequeathing him Identity, who inbred with Nuclear Family and Industrialism to spawn Homophobia.

Dean Kiley

Offline milker

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Re: Can anyone help with logs.
« Reply #1 on: June 09, 2007, 02:37:20 AM »
Extremely basically, a logarithm multiplies the effect of an addition.

Example:

2+2 = 4
2+2+2 = 6

2 power 2 = 4
2 power 2+2 = 16

So here the power of 2+2 has a dramatic effect when added as a multiplication compared to a single addition.

That's a VERY VERY BASIC explanation.

Milker.
mid-dec: stupid ass
mid-jan: seroconversion
mid-feb: poz
mar 07: cd4 432 (35%) vl 54000
may 07: cd4 399 (28%) vl 27760
jul 07: cd4 403 (26%) vl 99241
oct 07: cd4 353 (24%) vl 29993
jan 08: cd4 332 (26%) vl 33308
mar 08: cd4 392 (23%) vl 75548
jun 08: cd4 325 (27%) vl 45880
oct 08: cd4 197 (20%) vl 154000 <== aids diagnosis
nov 2 08 start Atripla
nov 30 08: cd4 478 (23%) vl 1880 !!!!!!!!!!!!!!!!!!!!!!!!!!
feb 19 09: cd4 398 (24%) vl 430 getting there!
apr 23 09: cd4 604 (29%) vl 50 woohoo :D :D
jul 30 09: cd4 512 (29%) vl undetectable :D :D
may 27 10: cd4 655 (32%) vl undetectable :D :D

Now accepting applications from blowjob ninjas™

Offline Tempeboy

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Re: Can anyone help with logs.
« Reply #2 on: June 09, 2007, 02:52:29 AM »
So far so good, could you do that one again with multiplication signs?  cheers.  and, with regard to viral loads expressed in logs, are we talking to the power of 10? and what does that mean?

 :-\
Roughly roundabout somewhere in the eighteenth or nineteenth century, Sodomite begat Homosexual out of moral, medical and legal models, bequeathing him Identity, who inbred with Nuclear Family and Industrialism to spawn Homophobia.

Dean Kiley

Offline Matty the Damned

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Re: Can anyone help with logs.
« Reply #3 on: June 09, 2007, 03:13:43 AM »
Tempe,

Matty the Damned is no expert when it comes to teh mathematix but he understands that logs are used to track HIV VL test results because we're focusing on trends over time. As you'd know one absolute VL result means very little and a variation which seems big (ie moving from 20,000 to 50,000) actually indicates no real change at all.

Essentially a shift of 2 log is a 99% change and in Australia is taken as clinically significant.

Or something like that.

MtD

Offline trellium

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Re: Can anyone help with logs.
« Reply #4 on: June 09, 2007, 03:35:32 AM »
for calculation of viral load, a base of 10 is used in the calculation:

log 10 = 1        that’s just 10 by itself
log 100 = 2       that’s 10 x 10
log 1000 = 3     that's 10 x 10 x 10 
log 10,000 = 4    that's 10 x 10 x 10 x 10
log 100,000 = 5    that's 10 x 10 x 10 x 10 x 10 (u get the idea...)

so for someone with a viral load of say 4.5 log, that's in the range of tens of thousands copies of those annoying f*uckers
and a viral load of say 5.6 log will be in the range of hundreds of thousands of those nasty f*uckers

to calculate the log expression of your viral load say 27,760  enter "27760" -->  press the LOG button on your scientific calculator.
I use the one that comes with MS Windoz on my computer, or just enter "log 27760" at google.com and it'll give u the answer of 4.44341946

to calculate your viral load from a given log expression say 4.5, enter "4.5" --> press INV (Inverse)  --> press LOG button on the scientific calculator (google can't do inverse log calculation yet) (oops! my bad) :P and that'll give u the answer of 31622 copies of the virus

Due to the margin of error for the VL test, there has to be at least a difference of 0.3 log to have any significance.
« Last Edit: June 09, 2007, 08:39:09 AM by trellium »

Offline newt

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Re: Can anyone help with logs.
« Reply #5 on: June 09, 2007, 06:17:18 AM »
In terms of viral load...

viral load of 50 copies = 1.7 log value
500 = 2.7
5,000 = 3.7
50,000 = 4.7
500,000 = 5.7

etc

Strictly speaking its a log10 value ie 10log = number eg 101.7 = 50 or thereabouts, 101 = 10, 102 = 100 etc.

To convert your viral load in to the log version type "log(viral load here)" into the Google search box and hit ENTER

- matt
« Last Edit: June 09, 2007, 06:20:15 AM by newt »
"The object is to be a well patient, not a good patient"

Offline newt

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Re: Can anyone help with logs.
« Reply #6 on: June 09, 2007, 06:46:41 AM »
Google can do reverse calculations.

Type "10^log value" into the search box eg "10^1.7" returns 50 and a tiny bit, "10^2" returns 100.

- matt
« Last Edit: June 09, 2007, 03:10:12 PM by newt »
"The object is to be a well patient, not a good patient"

Offline milker

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Re: Can anyone help with logs.
« Reply #7 on: June 09, 2007, 12:38:19 PM »
In terms of viral load, using the log gives a better picture than using absolute numbers. You can think of the VL scale going from 1 to 6, 1 being very good, 6 being bad. It's a lot easier to use a small scale like this rather than trying to figure out if 20000 is better than 50000, to take Matty's example:

log(20000) = 4.3
log(50000) = 4.6

In a scale of 1 to 6, a VL change from 4.6 to 4.3 is not very significant.

Does that make it better to understand?

Milker.

mid-dec: stupid ass
mid-jan: seroconversion
mid-feb: poz
mar 07: cd4 432 (35%) vl 54000
may 07: cd4 399 (28%) vl 27760
jul 07: cd4 403 (26%) vl 99241
oct 07: cd4 353 (24%) vl 29993
jan 08: cd4 332 (26%) vl 33308
mar 08: cd4 392 (23%) vl 75548
jun 08: cd4 325 (27%) vl 45880
oct 08: cd4 197 (20%) vl 154000 <== aids diagnosis
nov 2 08 start Atripla
nov 30 08: cd4 478 (23%) vl 1880 !!!!!!!!!!!!!!!!!!!!!!!!!!
feb 19 09: cd4 398 (24%) vl 430 getting there!
apr 23 09: cd4 604 (29%) vl 50 woohoo :D :D
jul 30 09: cd4 512 (29%) vl undetectable :D :D
may 27 10: cd4 655 (32%) vl undetectable :D :D

Now accepting applications from blowjob ninjas™

Offline marc11864

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Re: Can anyone help with logs.
« Reply #8 on: June 09, 2007, 02:22:14 PM »
My head hurtz  ???
Let us cavort like the Greeks of old! You know the ones I mean.

Offline fearless

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Re: Can anyone help with logs.
« Reply #9 on: June 11, 2007, 10:52:31 PM »
A nice simple explanation:

A scale in which equal percentage changes are represented by equal distances.

A logarithmic scale works great for numbers that increase exponentially, as it represents the change in a more manageable way.

With respect to viral loads, a logarithmic representation shows that a change from a viral load of 10 to 100 has the same significance as a change to viral load of 1,000 to 10,000. That is, in both cases the change has been ten-fold, or 1 log scale.
However, if you were to do a linear graph of these two changes the change from 1,000 to 10,000 would seem much greater than the change from 10 to 100.
(see attached graphs)

hope that makes some kind of sense as to why we use them



[attachment deleted by admin]
« Last Edit: June 12, 2007, 12:06:50 AM by fearless »
Be forgiving, be grateful, be optimistic

 


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