Forex Questions and Answers - FXAnswer

Linear elasticity as a general three-dimensional theory began to be developed in the early 1820s based on Cauchy’s work. Simultaneously, Navier had developed an elasticity theory based on a simple corpuscular, or particle, model of matter in which particles interacted with their neighbours by a central force attraction between particle pairs. As was gradually realized, following work by Navier, Cauchy, and Poisson in the 1820s and ’30s, the particle model is too simple and makes predictions concerning relations among elastic moduli that are not met by experiment.

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A linear price scale is plotted on the side of the chart so that there is an equal distance between the prices, and each unit change on the chart is represented by the same vertical distance on the scale, regardless of what price level the asset is at when the change occurs. By contrast, a logarithmic price scale is plotted so that the prices in the scale are not positioned equidistantly; instead, the scale is plotted in such a way that two equal percent changes are plotted as the same vertical distance on the scale.
An increase in price from $10 to $15 is the same as an increase from $20 to $25 on the linear chart because both scenarios represent an increase of $5. However, a logarithmic price scale will show the vertical distance between $10 and $15 to be different than the $5 distance between $20 to $25. The reason for this is that a change of $5 (when the price is at $10) represents a 50% increase, while a move from $20 to $25 is a 25% increase. Since a 50% increase is more significant than 25%, chartists will use a larger distance between the prices to clearly show the magnitude of the changes. When using a logarithmic scale, the vertical distance between the prices in the scale will be equal when the percent change between the values is the same.
In general, most traders and charting programs use the logarithmic scale, but it is always a good idea to explore other approaches to determine which is the most suitable for your trading style.

It is nice to see a simple linear chart with dollar numbers that is easy to calculate. However, linear price scale may not be good for significant changes in stock prices if we calculate money in terms of return on investment (ROI). For example, the change $10 of SP-500 gives around 10% market performance in 1970 but the same $10 change is equivalent only 1% of SP-500 performance in 2010.

Using Logarithmic Price Scale for Stock Performance

So that be aware that big changes on linear graph can be misleading since they may not represent big ROI. That is why logarithmic (log) price scales are used by many investors and technical traders. Log scale graphs correctly show in the percentage the rate of return-on-investment for both, small and big changes in prices. Log graphs show percentage changes accurately, since the same interval anywhere on the price scale represents the same percentage change.

Logarithmic price scale is when the price scale (usually on the vertical axis) is skewed so that a given distance always represents the same percentage change in price, rather than the same absolute change in price (as is the case for a linear chart). In other words, the distance from 1 to 10 is the same as the distance from 10 to 100 on a logarithmic chart, but the latter distance is ten times greater on a linear chart.

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What Does Logarithmic Price Scale Mean?
A type of scale used on a chart that is plotted in such a way that two equivalent percent changes are represented by the same vertical distance on the scale, regardless of what the price of the asset is when the change occurs. The distance between the numbers on the scale decreases as the price of the underlying asset increases. This is the case because a $1 increase in price becomes less influential as the price heads higher since it now corresponds to less of a percentage change than it did when the price of the asset was at a lower level. Also referred to as a "log scale".

Logarithmic price scales are generally accepted as the default setting for most charting services, and they're used by the majority of technical traders. Common percent changes are represented by an equal spacing between the numbers in the scale. For example, the distance between $10 and $20 is equal to the distance between $20 and $40 because both scenarios represent a 100% increase in price. Contrast this to "linear price scale".

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