# logarithmic scale

#### kubeek

Joined Sep 20, 2005
5,785

#### wayneh

Joined Sep 9, 2010
17,269
Yes, I'm not sure their is precise language for this. A true log plot is log(y) versus x, and a log-log is log(y) against log(x). Plotting y against log(x) is called...?

"Exponential" makes sense but most people wouldn't understand if you refer to it this way.

#### Papabravo

Joined Feb 24, 2006
20,133
Would you feel better if the logarithmic axes were labeled with the actual logarithm values. If you wanted an exponential axis it might be labeled with exponential values

#### GopherT

Joined Nov 23, 2012
8,009
This is a "frame of reference" issue.
The resistance is the exponential of the rotation of the potentiometer, or,
The log of the resistance is the rotation position.

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#### MrAl

Joined Jun 17, 2014
10,079
Hi,

The x axis distance is compressed in a manner consistent with a log function.

For example, the distance of a linear scale:
1,2,3,4,5,6,7,8,..all numbers up fo 1000 (which for unit distance takes up a width of 999 units)

is compressed into a much shorter distance:
0,10,100,1000, (only 3 units wide)

so we went from 0 to 1000 with the log scale in the same distance as we went from 1 to just 4 in the linear scale. That's what the log function does too because when we take the log of bigger numbers we still get a smaller number yet retain all the same information.

For the y axis, we just take the log before plotting in most cases or scale it with a constant factor also: Vdb=20*log(V).

• anhnha

#### joeyd999

Joined Jun 6, 2011
4,816
• anhnha

#### wayneh

Joined Sep 9, 2010
17,269
• joeyd999

#### DGElder

Joined Apr 3, 2016
351
This has been bothering me for some time, why is the logarithmic scale such as this one https://www.cs.sfu.ca/~tamaras/digitalAudio/Linear_vs_logarithmic.html called logarithmic, when the values on the scale increase exponentialy, so in my opinion should be called an exponential scale?
It is called a log scale because of the relative distances between the scale marks on the graph, not the associated values for those marks.
For example the distance between plot values of 10 and 100 is the same distance as between 100 and 1000 on a log scale, because the distances are based on the logs of those values. If it were linear the 100-1000 distance would be 10 times greater than the 10-100 distance.

If you plot an exponential function on log paper the plot will appear linear.

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• anhnha, killivolt and nsaspook