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If a number, x, is expressed as a power of another number, y, that is, if x = yn, then n is said to be the logarithm of x to base y. Common logarithms are to the base 10; natural or Napierian logarithms are to the base e, a mathematical constant.
[G. logos, word, ratio, + arithmos, number]


a mathematical device.

common logarithm
the value of the power when a number is expressed as to the power of 10 (has the base 10). Thus 100 expressed as to the power of 10 is 102 and the log of 100 is 2.
Napierian logarithm
see natural logarithm (below).
natural logarithm
as for common logarithm, except that the base is e or 2.178. Called also Napierian logarithm.
References in periodicals archive ?
Similarly, the logarithmical averages of sales in 2008 in Japan are also depicted by crosses.
A bipolar transconductor implements a hyperbolic tangent function F [3, 9] as relations (16) show and its inverse is a logarithmical function (17)
For 56% of those with a modified correction, there was an improvement in distance visual acuity of at least one logarithmical step (or one line on the acuity chart); for 1 person, distance visual acuity improved seven logarithmical steps.
The cardiac vagal reactivity in response to orthostasis was evaluated as percentual change of logarithmical spectral power in high frequency band (as index of vagal modulation) using mathematical expression: [(logHF power in standing position--logHF power in the 1st supine position) / logHF power in the 1st supine position] x 100 (%).
Bottom region with linear temperature profile and upper region which is temperature variation in shape logarithmical approximately.
Xenakis has already worked with this kind of spirals that include both logarithmical and exponential acceleration patterns in Terretektorh.
10) were calculated for 67 values of r spread over the interval <4, 75> equidistantly in logarithmical scale, and for 15 values of q equidistantly spread in the interval <0, 15> giving a total of 1005 features for each image.