Lehmer mean
In mathematics, the Lehmer mean of a tuple of positive real numbers, named after Derrick Henry Lehmer, is defined as:
The weighted Lehmer mean with respect to a tuple of positive weights is defined as:
The Lehmer mean is an alternative to power means
for interpolating between minimum and maximum via arithmetic mean and harmonic mean.
Properties
The derivative of is non-negativethus this function is monotonic and the inequality
holds.
The derivative of the weighted Lehmer mean is:
Special cases
- is the minimum of the elements of.
- is the harmonic mean.
- is the geometric mean of the two values and.
- is the arithmetic mean.
- is the contraharmonic mean.
- is the maximum of the elements of. Sketch of a proof: Without loss of generality let be the values which equal the maximum. Then
Applications
Signal processing
Like a power mean, a Lehmer mean serves a non-linear moving average which is shifted towards small signal values for small and emphasizes big signal values for big. Given an efficient implementation of a moving arithmetic mean called you can implement a moving Lehmer mean according to the following Haskell code.lehmerSmooth :: Floating a => -> a -> ->
lehmerSmooth smooth p xs =
zipWith
)
- For big it can serve an envelope detector on a rectified signal.
- For small it can serve an baseline detector on a mass spectrum.
Q=0 is the arithmetic mean. Positive Q can reduce pepper noise and negative Q can reduce salt noise.